Communication And Networking - Hack to Learn

PoisonTap - siphons cookies, exposes internal router & installs web backdoor on locked computers

2016-11-17T22:51:00.002+08:00

Created by @SamyKamkar || https://samy.pl
Source code: https://github.com/samyk/poisontap

When PoisonTap (Raspberry Pi Zero & Node.js) is plugged into a locked/password protected computer, it:

emulates an Ethernet device over USB (or Thunderbolt)
hijacks all Internet traffic from the machine (despite being a low priority/unknown network interface)
siphons and stores HTTP cookies and sessions from the web browser for the Alexa top 1,000,000 websites
exposes the internal router to the attacker, making it accessible remotely via outbound WebSocket and DNS rebinding (thanks Matt Austin for rebinding idea!)
installs a persistent web-based backdoor in HTTP cache for hundreds of thousands of domains and common Javascript CDN URLs, all with access to the user’s cookies via cache poisoning
allows attacker to remotely force the user to make HTTP requests and proxy back responses (GET & POSTs) with the user’s cookies on any backdoored domain
does not require the machine to be unlocked
backdoors and remote access persist even after device is removed and attacker sashays away

Live demonstration and more details available in the video:

PoisonTap evades the following security mechanisms:

Password Protected Lock Screens
Routing Table priority and network interface Service Order
Same-Origin Policy
X-Frame-Options
HttpOnly Cookies
SameSite cookie attribute
Two-Factor/Multi-Factor Authentication (2FA/MFA)
DNS Pinning
Cross-Origin Resource Sharing (CORS)
HTTPS cookie protection when Secure cookie flag & HSTS not enabled

PoisonTap

PoisonTap is built for the $5 Raspberry Pi Zero without any additional components other than a micro-USB cable & microSD card, but can work on other devices that can emulate USB gadgets such as USB Armory and LAN Turtle.

(incredible HTML5 canvas animation by Ara)

Video Demo: https://youtu.be/Aatp5gCskvk

Point of Contact: @SamyKamkar // https://samy.pl

Released: November 16, 2016

Source code and download: https://github.com/samyk/poisontap

How hacker crack your password

2016-11-07T22:43:00.000+08:00

Original Title: Beware! This are the 6 ways by which hackers crack your Password

If your bank account or online accounts like Gmail, Yahoo, Facebook or Twitter has ever been hacked, you should know that the cyber criminals use specific trick to get into your account. With passwords being the central theme of almost all your accounts, hackers prefer to go after your password to hack into your financial as well as online accounts.

If your account is hacked, the criminals probably used one of the 6 below given ways to crack your account. If you study these methods you can prepare yourself better to repel such hacks and control your accounts easily.

Brute force attack

Brute force is about overpowering the computer’s defenses by using repetition. Brute force attack is a random trial and error method hack repeated till the password is finally cracked. Hackers randomly keep applying names and numbers to crack password through this pattern. Sometimes, a lot of guesswork is also used to decode password. Arithmetic numbers, birth date, pet’s name, favourite actor’s name are the password that users commonly use.

Dictionary Hacking

Dictionary hacking is also a form of brute force attack. But in Dictionary hack, hackers use various permutations and combinations of dictionary words. They repetitively use the dictionary software and try various combination of words to crack your password. A report says, over 50 percent of the passwords are cracked through this process.

Brute force dictionaries always start with simple letters “a”, “aa”, “aaa”, and then eventually moves to full words like “dog”, “doggie”, “doggy”. These brute force dictionaries can make up to 50 attempts per minute in some cases.

Phishing

Phishing is another most commonly used tool of hackers to to acquire usernames and passwords. Also, phishing is the most used method because it takes just a trick to fool the victim into divulging his/her login credentials. Most trojans spread through phishing while sometimes hackers create cloned websites or fake internet address is created wherein you are asked to fill in your username and password details.

Phishing is the attempt to acquire sensitive information such as usernames, passwords, and credit card details (and sometimes, indirectly, money), often for malicious reasons, by masquerading as a trustworthy entity in an electronic communication.

Spidering attack

Another hacking tool is the Spidering attack. Just as the name suggests, hackers also crawl your website like a spider and collect all the common information. Cyber criminals normally use spidering attack to target big companies.

A spider is a tool that crawls a website looking for all the available content. There’s a few different ways to discover content:

– Static Content
– Dirbuster
– HTTP Method
– Ascension Fuzz
– Query Fuzz
– Cookie Fuzz
– Robots.txt / Sitemap.xml
– RIA Checks
– UserAgent
– Regexp path/url
– Public cache search
– /status

Keylogger attack

This hacking tool is very similar to Phishing and is generally spread through malware infection. The victim is usually trapped into installing a keylogger on his/her PC/Laptop by clicking on an attachment is sent to victim email. The moment you download the attachment, it scans through your browser. Once installed, the keylogger records all your Internet activity which is than relayed back to the command and control servers.

Rainbow Table

While you might think of Rainbow Tables as eclectic colorful furniture, those aren’t the ones we are going to discuss. The Rainbow Tables that we are talking about are used to crack passwords and are yet another tool in the hacker’s ever growing arsenal.

This method requires a good knowledge of computers and coding.Rainbow Tables are basically huge sets of precomputed tables filled with hash values that are pre-matched to possible plaintext passwords. The Rainbow Tables essentially allow hackers to reverse the hashing function to determine what the plaintext password might be. It’s possible for two different passwords to result in the same hash so it’s not important to find out what the original password was, just as long as it has the same hash. The plaintext password may not even be the same password that was created by the user, but as long as the hash is matched, then it doesn’t matter what the original password was.

The use of Rainbow Tables allow for passwords to be cracked in a very short amount of time compared with brute-force methods, however, the trade-off is that it takes a lot of storage (sometimes Terabytes) to hold the Rainbow Tables themselves, Storage these days is plentiful and cheap so this is not a big issue for hackers. You can also get precomputed Rainbow Tables for cracking passwords of vulnerable operating systems such as Windows XP, Vista, Windows 7, and applications using MD5 and SHA1 as their password hashing mechanism (many web application developers still use these hashing algorithms).

Credits to Vijay Prabhu
Do drop in your comments about the above six methods of password cracking.

Find ip address in windows 7 using command prompt

2016-11-05T22:40:00.000+08:00

The fastest way to check your computer ip address in windows 7 using cmd.exe

At Start, search for cmd.exe. Select to run the cmd.exe

Type ipconfig in the cmd.exe. Then press enter.

You may see some result shown in the command prompt. Search for wireless if you are currently connected to wireless network, else look for local area network Ethernet adapter

Congratulations. The IPv4 as shown is the computer local area network ip address. And this is the easiest and fastest way to find ip address in windows 7 using command ipconfig.

2014 Exam Answers - CCNA 1 Chapter 8 v5 0

2014-10-19T10:58:00.003+08:00

1

Fill in the blank.

The decimal equivalent of the binary number 10010101 is ”149” .

2

Place the options in the following order:

[+] 192.168.100.161/25

[+] 203.0.113.100/24

[+] 10.0.50.10/30

[#] 192.168.1.80/29

[#] 172.110.12.64/28

[#] 10.10.10.128/25

[*] 10.0.0.159/27

[*] 192.168.1.191/26

[+] Order does not matter within this group.

[#] Order does not matter within this group.

[*] Order does not matter within this group.

3

What is indicated by a successful ping to the ::1 IPv6 address?

The link-local address is correctly configured.

The default gateway address is correctly configured.

The host is cabled properly.

All hosts on the local link are available.

IP is properly installed on the host.*

4

Launch PT - Hide and Save PT

Open the PT Activity. Perform the tasks in the activity instructions and then answer the question.

Which message is displayed on the web server?

Correct configuration!*

IPv6 address configured!

You did it right!

Successful configuration!

5

Which two ICMP messages are used by both IPv4 and IPv6 protocols? (Choose two.)

router solicitation

protocol unreachable*

neighbor solicitation

route redirection*

router advertisement

6

A message is sent to all hosts on a remote network. Which type of message is it?

unicast

directed broadcast*

limited broadcast

multicast

7

Which two things can be determined by using the ping command? (Choose two.)

the average time it takes each router in the path between source and destination to respond

the average time it takes a packet to reach the destination and for the response to return to the source*

whether or not the destination device is reachable through the network*

the IP address of the router nearest the destination device

the number of routers between the source and destination device

8

A DHCP server is used to assign IP addresses dynamically to the hosts on a network. The address pool is configured with 192.168.10.0/24. There are 3 printers on this network that need to use reserved static IP addresses from the pool. How many IP addresses in the pool are left to be assigned to other hosts?

253

252

251*

254

9

Which two parts are components of an IPv4 address? (Choose two.)

logical portion

network portion*

physical portion

broadcast portion

host portion*

subnet portion

10

Which IPv6 address is most compressed for the full FE80:0:0:0:2AA:FF:FE9A:4CA3 address?

FE80::2AA:FF:FE9A:4CA3*

FE80::0:2AA:FF:FE9A:4CA3

FE80:::0:2AA:FF:FE9A:4CA3

FE8::2AA:FF:FE9A:4CA3

11

12

What are three parts of an IPv6 global unicast address? (Choose three.)

an interface ID that is used to identify the local host on the network*

an interface ID that is used to identify the local network for a particular host

a subnet ID that is used to identify networks inside of the local enterprise site*

a global routing prefix that is used to identify the network portion of the address that has been provided by an ISP*

a global routing prefix that is used to identify the portion of the network address provided by a local administrator

13

14

Which network migration technique encapsulates IPv6 packets inside IPv4 packets to carry them over IPv4 network infrastructures?

encapsulation

translation

dual-stack

tunneling*

15

When an IPv6 enabled host needs to discover the MAC address of an intended IPv6 destination, which destination address is used by the source host in the NS message?

global unicast address of the receiver

solicited-node multicast address*

all-node multicast address

link-local address of the receiver

16

When a Cisco router is being moved from an IPv4 network to a complete IPv6 environment, which series of commands would correctly enable IPv6 forwarding and interface addressing?

Router# configure terminal

Router(config)# interface fastethernet 0/0

Router(config-if)# ip address 192.168.1.254 255.255.255.0

Router(config-if)# no shutdown

Router(config-if)# exit

Router(config)# ipv6 unicast-routing

Router# configure terminal

Router(config)# interface fastethernet 0/0

Router(config-if)# ipv6 address 2001:db8:bced:1::9/64

Router(config-if)# no shutdown

Router(config-if)# exit

Router(config)# ipv6 unicast-routing ***********

Router# configure terminal

Router(config)# interface fastethernet 0/0

Router(config-if)# ipv6 address 2001:db8:bced:1::9/64

Router(config-if)# no shutdown

Router# configure terminal

Router(config)# interface fastethernet 0/0

Router(config-if)# ip address 2001:db8:bced:1::9/64

Router(config-if)# ip address 192.168.1.254 255.255.255.0

Router(config-if)# no shutdown

17

What two statements describe characteristics of Layer 3 broadcasts? (Choose two.)

There is a broadcast domain on each switch interface.

Routers create broadcast domains.*

A router will not forward any type of Layer 3 broadcast packet.

Broadcasts are a threat and users must avoid using protocols that implement them.

A limited broadcast packet has a destination IP address of 255.255.255.255.*

Some IPv6 protocols use broadcasts.

18

Which two statements are correct about IPv4 and IPv6 addresses? (Choose two.)

IPv6 addresses are represented by hexadecimal numbers.*

IPv6 addresses are 32 bits in length.

IPv4 addresses are 128 bits in length.

IPv4 addresses are represented by hexadecimal numbers.

IPv4 addresses are 32 bits in length.*

IPv6 addresses are 64 bits in length.

19

What is the prefix length notation for the subnet mask 255.255.255.224?

/26

/28

/27*

/25

20

Fill in the blank.

What is the decimal equivalent of the hex number 0x3F? “63”

21

What are two types of IPv6 unicast addresses? (Choose two.)

anycast

link-local*

multicast

loopback*

broadcast

22

When will a router drop a traceroute packet?

when the router receives an ICMP Time Exceeded message

when the host responds with an ICMP Echo Reply message

when the value in the TTL field reaches zero*

when the values of both the Echo Request and Echo Reply messages reach zero

when the RTT value reaches zero

23

An IPv6 enabled device sends a data packet with the destination address of FF02::1. What is the target of this packet?

all IPv6 configured routers across the network

all IPv6 configured routers on the local link

all IPv6 enabled nodes on the local link*

all IPv6 DHCP servers

24

How many bits are in an IPv4 address?

256

128

64

32*

CCNA 4 R&S Year 2014: Connecting Networks Chapter 1 v5.0 Exam Question with Answers

2014-03-10T23:20:00.000+08:00

Connecting Networks Chapter 1 v5.0 Exam Answers 2014

1
What are two structured engineering principles necessary for successful implementation of a network design? (Choose two.)

modularity*
security
availability
quality of service
resiliency*

2
What is an important first consideration when starting to design a network?

size of the network*
access security
protocols to be used
type of applications

3
Which layer of the Cisco Collaboration Architecture contains unified communications and conference software such as Cisco WebEx Meetings, WebEx Social, Cisco Jabber, and TelePresence?

service provider edge
enterprise WAN
applications and devices*
services module

4
In which layer of the hierarchical enterprise LAN design model would PoE for VoIP phones and access points be considered?

core
physical
data link
access*
distribution

5
Which network module is the fundamental component of a campus design?

access-distribution module*
services module
data center
enterprise edge

6
In a hierarchical network design, which layers may be combined into a collapsed core for smaller networks?

core, distribution, and access
distribution and access
core and access
core and distribution*

Refer to the exhibit. Which type of ISP connectivity to the service provider edge is being used by company A?

dual-homed
dual-multihomed
single-homed
multihomed*

8
What is one advantage to designing networks in building block fashion for large companies?

mobility
redundancy
increased network access time
failure isolation*

9
A network engineer wants to redesign the wireless network and make use of wireless network controllers that manage the many deployed wireless access points. In which network design module of the campus network architecture would the centralized wireless network controllers be found?

services*
access-distribution
enterprise edge
data center

10
Which two devices would commonly be found at the access layer of the hierarchical enterprise LAN design model? (Choose two.)

Layer 3 device
firewall
access point*
Layer 2 switch*
modular switch

11
Which approach in networking allows for network changes, upgrades, or the introduction of new services in a controlled and staged fashion?

modular*
network module
borderless
static

Refer to the exhibit. Which type of Cisco hierarchical LAN design model is used at school site 1?

7 layer
two-tier collapsed core*
three-tier
3 layer

13
Which three network architectures have been introduced by Cisco to address the emerging technology challenges created by the evolving business models? (Choose three.)

Cisco Collaboration*
Cisco Data Center*
Cisco Borderless*
Cisco Enterprise Edge
Cisco Enterprise Campus
Cisco Enterprise Branch

14
Which Cisco technology allows diverse network devices to connect securely, reliably, and seamlessly to enterprise network resources?

Cisco AnyConnect*
enterprise edge
building distribution
service provider edge

15
The network design for a college with users at five sites is being developed. Where in the campus network architecture would servers used by all users be located?

services
enterprise edge
data center*
access-distribution

16
What is creating a new challenge for IT departments by changing the border of the enterprise network?

tablets*
company-owned desktops
energy costs
access layer switching

17
Which network architecture functions through a combination of technologies that include wired, wireless, security, and more?

Cisco Borderless*
Cisco Enterprise Campus
Cisco Enterprise Edge
Cisco Enterprise Branch

18
Which network architecture combines individual components to provide a comprehensive solution allowing people to cooperate and contribute to the production of something?

Cisco Enterprise Campus Architecture
Cisco Enterprise Branch Architecture
Cisco Borderless Network Architecture
Cisco Collaboration Architecture*

19
Fill in the blank.
Reducing the complexity of network design by dividing a network into smaller
areas is an example of a ” hierarchical ” network model.

20
Fill in the blank. Use the abbreviation.
Under the Cisco Enterprise Edge module, the submodule that provides remote access
including authentication and IPS appliances is the ” VPN ” and remote access submodule.

Place the options in the following order:

- not scored –
core
ccess
distribution

JAN2012 - Chapter 1 CCNA Exploration 4.0 EWAN Answer and Question

2013-03-09T16:18:00.004+08:00

1. Which statement is true about the differences between a WAN and a LAN?
WANs generally support higher bandwidth than LANs support.
A WAN link typically traverses shorter geographic distances than a LAN link traverses.
A WAN often relies on the services of carriers, such as telephone or cable companies, but a LAN does not.
All WAN implementations generally use the same Layer 2 protocol but there are many accepted LAN Layer 2 protocols in use.

2. A U.S. company requires a WAN connection used only to transfer sales data from individual stores to the home office. All transfers will occur after business hours. The required bandwidth for this connection is estimated to be less than 38 kbps. Which type of connection requires the least investment for this company?
ATM
ISDN
analog dialup
T1 Leased Line

3. What are two advantages of an analog PSTN WAN connection? (Choose two.)
low cost
availability
traffic encryption
available bandwidth
support for voice and video

4. Which WAN technology uses a fixed payload of 48 bytes and is transported across both switched and permanent virtual circuits?
ATM
ISDN
Frame Relay
metro Ethernet

5. Which three WAN devices can be found in the cloud? (Choose three.)
ATM switches
core routers
CSU/DSU
Ethernet switches
Frame Relay switches
repeaters

6. Which term describes a device that will put data on the local loop?
DLCI
DTE
DCE
BRI
PRI

7. What is an advantage of packet-switched technology over circuit-switched technology?
Packet-switched networks are less susceptible to jitter than circuit-switched networks are.
Packet-switched networks can efficiently use multiple routes inside a service provider network.
Packet-switched networks do not require an expensive permanent connection to each endpoint.
Packet-switched networks usually experience lower latency than circuit-switched networks experience.

8. Which statement is true about data connectivity between a customer and a service provider?
Normally the CSU/DSU is the designated demarcation point for the service provider but not the customer.
The segment between the demarcation point and the central office is known as the “last mile.”
The local loop is the segment between the CSU/DSU and the serial port on a router.
Putting data on the local loop is the responsibility of the DTE.

9. A company needs a WAN connection that is capable of transferring voice, video, and data at a minimum data rate of 155 Mbps. Which WAN connection is the best choice?
X.25
DSL
ATM
ISDN BRI
ISDN PRI

10. Which statement is true of the functionality of the layers in the hierarchical network model?
The purpose of the access layer is to provide very high bandwidth communications between network devices.
Most security screening to prevent unauthorized entry to the network happens at the core layer.
Untrusted external connections are segmented from the rest of the network at all three levels.
The distribution layer aggregates WAN connections at the edge of the campus.

11. Why is the call setup time of a circuit-switched WAN implementation considered a drawback?
Routing protocols are incompatible with this function.
It restricts the communication sent to voice traffic only.
A telephone must be used to initially start transferring data.
Data cannot be transferred until a circuit has been established.

12. For digital lines, which device is used to establish the communications link between the customer equipment and the local loop?
CSU/DSU
Frame Relay switch
ISDN switch
modem
PBX switch

13. Which packet-switched WAN technology offers high-bandwidth connectivity capable of managing data, voice, and video all on the same infrastructure?
Time Division Multiplexing (TDM)
metro Ethernet
Integrated Services Digital Network (ISDN)
Public Switched Telephone Network (PSTN)

14. Which networking device is typically used to concentrate the dial-in and dial-out traffic of multiple users to and from a network?
core router
access server
Frame Relay switch
ATM switch

15. Which two devices are commonly used as data communications equipment? (Choose two.)
modem
router
CSU/DSU
ISDN switch
Ethernet switch

16. Which two features are identified with Frame Relay connections? (Choose two.)
53-byte cells
DLCI
DSLAM
PVC
SPID

17. Which statement about WAN protocols is correct?
ATM differs from other WAN protocols in that it uses variably sized packets.
Most WAN protocols use HDLC or a variant of HDLC as a framing mechanism.
The frame header consists of the frame check sequence and cyclic redundancy check.
ISDN differs from Frame Relay, HDLC, and ATM in that it is packet-switched rather than circuit-switched technology.

18. Which switching type will allow the communication devices in the provider network to be shared and only allocated to an individual subscriber during data transfer?
circuit-switched
dedicated switched lines
frame-switched
packet-switched

19. What can cause a reduction in available bandwidth on a cable broadband connection?
smaller cells
number of subscribers
committed information rate
distance from the central office of the provider

20. What three terms are associated with ISDN PRI? (Choose three.)
cell
DLCI
circuit switching
packet switching
data bearer channels
time-division multiplexing

21. At which two layers of the OSI model does a WAN operate? (Choose two.)
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Presentation Layer
Application Layer

22. What type of connectivity is established when VPNs are used from the remote site to the private network?
PVCs
DLCIs
tunnels
dedicated Layer 2 links

Update : Links

UCEN 3133 Advanced Computer Networks - Tutorial 5 - Year 2012

2012-05-19T19:43:00.000+08:00

Tutorial 5 – Routing and Traffic Engineering

1. Why is conventional IP routing mechanisms such as RIP incapable of supporting constraint based routing (CBR) ? Based on your answer:

(i) Explain why CBR routing is supported by a variant of link state routing protocols such as OSPF

(ii) Give two reasons why a MPLS network is particularly suited to support CBR

Constraint-based routing requires route calculation at the source as different sources may have different constraints for a path to the same destination, and the constraints associated with a particular source router are known only to that router, but not to any other router in a network. In IP routing such as RIP, every router in a network is involved in computation of a route is in a distributed fashion.

i) Link-State Routing Protocols floods the network with information about all links in the network (in addition to constraint-related information associated with that link), hence allowing the source router to perform the entire route calculation

ii) The LSRs within the core MPLS network only switch on the basis of these labels and no longer make any forwarding decisions of their own based on the IP header (which is what happens in conventional routing).

Mapping between an FEC and an LSP is completely confined to the edge LSR at the head end of the LSP. The decision as to which packets will take a particular explicit route is completely achieved by this edge LSR, noone else is involved.

2. What is the common additional feature used in extending RSVP and LDP to support CBR, and briefly explain how this feature is used as part of CR-LDP ?

The Explicit Route Object (ERO) contains the explicit route that the message has to take. Forwarding of a message containing a ERO by a router is determined not by the IP destination address, but the content of the ERO. The ERO consists of an ordered sequence of “hops,” where the sequence specifies an explicit route and each hop is represented by an “abstract node.”, which is a group of one or more routers

A LSR determines the explicit route to be established and constructs a ERO that contains this route.
This LSR then constructs a LDP LABEL REQUEST message and includes ERO in this message, and finds the first abstract node in ERO and forwards this message onwards to it.
The receiving LSR removes the abstract node associated with it and forwards it onwards to the next LSR specified in the ERO
This process is repeated until it finally arrives at the destination LSR.
This LSR then constructs a LABEL MAPPING message and sends it back on the same route – each LSR along the way will use the label to populate its label forwarding message.
When it reaches the original LSR, the labels would have established a complete LSP from the original LSR to the destination.

3. List 5 common traffic parameters that are part of the CR-LDP specification and briefly explain their purpose.

Peak data rate (PDR), Peak burst size (PBS)
Committed data rate (CDR), Committed burst size (CBS)
Excess burst size (EBS)

Peak data rate and burst size together define a token bucket, which characterizes the maximum rate of traffic that is expected to be sent down this LSP. Committed data rate and burst size define a token bucket characterizing the average rate at which traffic is expected to be sent on this LSP. Excess burst size defines another token bucket that can be used to characterize the amount by which bursts may exceed the committed burst size.

4. Resource reservation for QOS purposes using RSVP may cause problems in a MPLS network that uses link state routing protocols such as CSPF. Explain briefly the cause of this problem, and how it is addressed.

Establishing a route for a particular traffic flow may require resource reservation along the route using RSVP. Once resources (such as bandwidth) of a link are reserved, the attributes of these links will change (since bandwidth is usually one of the attributes). In link state routing protocols such as CSPF, when the attribute of a given link changes, the node to which the link is connected floods this information throughout the network. Since resource reservation happens quite frequently, flooding also happens frequently which results in high network overhead.

This can be addressed by establishing an upper bound on the frequency of flooding of information when a link attribute changes.

5. List the drawbacks of using RSVP and CR-LDP respectively in a MPLS network.

RSVP makes reservations for individual microflows between single applications, which does not scale well as the number of microflows in a large IP network is very large. RSVP’s soft state also requires constant refreshing which consumes bandwidth and processing resources.

CR-LDP, by contrast, runs on top of TCP. TCP’s congestion avoidance may limit the transfer of information between LSRs. There is overhead involved in establishing an adjacency between two LSRs because they must go through TCP’s handshake sequence before initiating an LDP session.

6. What is meant by a routing transient and name 2 factors that influence the duration of a routing transient within a network based on conventional IP routing

Routing transients refer to episodes in a network where routing information across a network is changing, mainly due to failures of links or routers or both. At such times, the routing information stored at different routers may be temporarily inconsistent.

The duration of routing transients depends on two factors: - The time it takes for a router adjacent to the failed link (or node) to detect the failure, and the time it takes to distribute this information among all the routers and for them to recompute their forwarding tables based on this information (converge on the failure).

7. What is the motivation behind the use of a protection LSP in a MPLS ? Briefly explain how it is set up and used in that context.

Protection LSPs are used to handle link failures in an MPLS, so that when a link fails, the LSR attached to that link can channel all traffic destined for that link on to the alternative protection LSP.

When a link between two LSRs fail, the information about this failure will be distributed (via OSPF or IS-IS) to all the LSR. Once the original LSR gets this information, it can use constraint-based routing to compute a new route (the protection LSR). Or it may already have a precomputed alternative route

To route traffic onto the new route, the LSR pushes a new label corresponding to the protection LSP into the label stack of all incoming packets, allowing them to be switched over the protection link.

8. The Constrained Shortest Path First (CSPF) algorithm is typically employed in a MPLS network for TE purposes during the construction of routing tables. In the process of constructing a routing table based on CSPF, what are the tiebreaking factors used to arbitrate between two paths of equal hop cost ?

For tie break

Take the path with the largest minimum available bandwidth.
If there is still a tie, take the path with the lowest hop count (the number of routers in the path).
If there is still a tie, take one path at random.

9. Consider a MPLS network of routers (A-E) as shown below. The parenthesis pair that labels each link between the routers is used to denote the hop cost and bandwidth available, respectively. For example, the link between A and B has a hop cost of 2 and a bandwidth of 90 Mbps. CSPF is now used to calculate the best path to router D from router A, given a constraining bandwidth of 70 Mbps. Show all steps involved in constructing router A’s table to determine this best path. In your working, show all tentative routes possible and mark them as cancelled if they do not qualify to be used.

Configured constraint 70 Mbps

PATH list	TENT List
{A, 0, self, N/A}

PATH list	TENT List
{A, 0, self, N/A}	{B, 2, B, 90} {C, 8, C, 80} {D, 10, D, 100}

PATH list	TENT List
{A, 0, self, N/A} {B, 2, B, 90}	{E, 3, B, 90} {C, 7, B, 90} [1] {C, 8, C, 80} -> cancel {D, 10, D, 100} {D, 10, B, 80} -> cancel

PATH list	TENT List
{A, 0, self, N/A} {B, 2, B, 90} {E, 3, B, 90}	{C, 7, B, 90} {D, 10, D, 100} {D, 10, B, 90} -> cancel [2]

PATH list	TENT List
{A, 0, self, N/A} {B, 2, B, 90} {E, 3, B, 90} {C, 7, B, 90}	{D, 10, D, 100} {D, 8, B, 50} -> cancel [3]

PATH list	TENT List
{A, 0, self, N/A} {B, 2, B, 90} {E, 3, B, 90} {C, 7, B, 90} {D, 10, D, 100}

[1] {C, 7, B, 90} – The required format is {destination, cost, next hop, minimum bandwidth}. If we take the newly added node to the PATH list {B, 2, B, 90}, this means that the destination is B, cost = 2, next hop to get to B is also B, and minimum bandwidth on all the routes to B is 90. Now when we consider connection to C from B, the entry for the TENT list becomes {C, 7, B, 90}. 90 because if we consider from A->B->C, the minimum bandwidth on all the links encountered is 90. The logic of taking the minimum bandwidth is that the delay along any given path is most affected by the link on that path with the smallest bandwidth. So if a packet was going from A -> C, the slowest travel time would be from A to B. Therefore, if we have two paths to C with exactly the same cost, then as a tie breaker we would pick the path with the highest bandwidth (remember the rule).

[2] {E, 3, B, 90} -> This means the shortest path to E from A has a total cost of 3, with next hop B, and minimum bandwidth among all the links so far is 90. E has a connection with metric {7,100} to D. So the total cost from A to D now becomes 10. The next hop is still B. The minimum bandwidth is still 90 (because the E-D bandwidth is 100). So, the correct entry becomes {D, 10, B, 90}, which is cancelled because its bandwidth is lower than the existing entry of {D, 10, D, 100} -> remember, in tie breaker we choose the one with the highest bandwidth

[3] {C, 7, B, 90} -> This means the shortest path to C from A has a total cost of 7, with next hop B, and minimum bandwidth among all the links so far is 90. C has a connection with metric {1,50} to D. So the total cost from A to D now becomes 8. The next hop is still B. The minimum bandwidth becomes 50 (because this is lower than the previous lowest of 90). So, the correct entry becomes {D, 8, B, 50}, which is cancelled because the bandwidth of 50 is less than the initial configured constraint of 70 as given in the question.

10. A multimedia network that provides QOS guarantees uses a leaky bucket policer in one of its routers to ensure that the incoming packet traffic does not exceed the TSpec specification agreed upon during an initial session of Integrated Services (IntServ). The following are the features of this policer:

· The token buffer can hold at most three (3) tokens, and is initially filled with two (2) tokens at time slot t = 0.

· New tokens arrive into the bucket at a rate of two (2) tokens per time slot. Packets arrive at the beginning of a time slot and enter the packet queue, where they are processed and transferred to the output link in a First In First Out (FIFO) manner.

· The size of the packet queue is four (i.e. it can queue a maximum of 4 packets at any given time slot); any extra arriving packets are dropped.

· Packets that obtain available tokens in a given time slot go together on the same time slot in the output link.

Time slot	Incoming Packets
0	A B C D
1	E F
2	G
3	-
4	-
5	H I J K
6	L M N O
7	P Q
8	-
9	R S T

The table shows incoming packets from the network into the router with the policer, from time slot t = 0 to time slot t = 9. Based on this information, construct a new table with columns showing the packets in queue, tokens in bucket and packets on output link from time slot t = 0 to t = 9.

Time slot	Packets in queue	Tokens in bucket	Packets at output
0	A B C D	2	A B
1	C D E F	2	C D
2	E F G	2	E F
3	G	2	G
4	-	3	-
5	H I J K	3	H I J
6	K L M N	2	K L
7	M N P Q	2	M N
8	P Q	2	P Q
9	R S T	2	R S

UCEN 3133 Advanced Computer Networks - Tutorial 4 - Year 2012

2012-05-17T19:41:00.000+08:00

Tutorial 4 – QOS and RSVP

1. List and briefly describe the activities that a router or switch is likely to engage in to provide a certain QOS guarantee in a network.

(i) Policing: verifying that incoming traffic conforms to its agreed specification

(ii) Admission control: checking to see if there are enough resources to meet a request for QoS

(iii) Classification: recognizing those packets that need particular levels of QoS

(iv) Queuing and scheduling: making decisions about when packets are transmitted and which packets are dropped that are consistent with the QoS guarantees

2. What is the primary difference between IntServ and DiffServ approaches to allocating resources for QOS purposes ? Which approach scales better for a large IP network and why ?

IntServ enables end-to-end QoS guarantees for a single flow (microflow) from one sender to one or more receivers through a signalling protocol like RSVP

DiffServ a coarse-grained model groups traffic of many different flows into several small classes and provides QOS guarantees on a per-class basis

DiffServ scales better. In a large IP network, the number of microflows is very large and to keep QOS and state information about each one provides a heavy burden on the routers in the network, making it difficult to scale. Grouping flows into classes allows easier management of QOS information.

3. In what way does the deficit round robin (DRR) approach provide for a more fairer QOS allocation of transmission resources on a router as compared to the weighted round robin approach ? Briefly explain how it works.

It computes weights allocated to different flows in terms of total bytes rather than number of packets. This is fairer QOS allocation because IP packets vary in size

DRR allocates a number of bytes to each flow. When a flow is selected, DRR transmits as many packets as possible without exceeding the allotted number of bytes.

The remainder (i.e. the difference between the number of bytes that was allocated and the size of the packets actually sent) becomes a deficit which is added to the amount that will be sent in the next round

4. Explain briefly how RSVP works with reference to the PATH and RESV messages.

(i) PATH messages travel from a sender to one or more receivers (explicitly designed to support multicast) and include TSpecs and classification information provided by the sender.

(ii) When a receiver gets a PATH message, it can send a RESV message back toward the sender. The RESV message identifies the session for which the reservation is to be made and indicates the level of QoS required by this receiver.

(iii) Messages are intercepted by every router along the path, so that resource allocation can take place at all the necessary hops.

(iv) Each router must agree to reserve the resources the request specifies. Reservation is unidirectional for a single flow direction

5. Three clients are receiving shared multicast video traffic flow across a MPLS network from a media server. The routes from these different client converge on a router that the server is directly connected to. All 3 clients make a QOS reservation requests for a delay latency of 30ms, 15 ms and 10 ms respectively to this router.

(i) How would RSVP handle these requests in the router ?

(ii) How does RSVP ensure that these reservation requests are propagated correctly across the MPLS network to this router at the transmitting end ?

i) These requests are merged into a single reservation request for the common flow, to which the router will select the smallest latency of 10ms

ii) When a path message in RSVP is sent to a client, each router at each hop inserts its own IP address as the message’s last hop. Each router can look at the last hop field to learn where the flow came from. Should it later receive a reservation request for this flow, this last hop information tells it where to send the reservation request next.

6. Explain briefly what the term soft state means within the context of RSVP. Consider an ongoing video conference involving 2 clients receiving multicast traffic from a central server. A new client wishes to join this multicast group. Outline the series of steps that it will undergo to achieve this, and show how soft state helps in this registration process.

Soft state means that PATH and RESV messages in RSVP must be sent periodically to refresh a reservation. If they are not sent for some interval (the time-out period), then the reservation is automatically torn down

The client sends an IGMP group membership report message to join this multicast group.
The local router receives this message and to update the rest of the network, the router builds an OSPF link state advertisement and floods it through the network. Once all routers are updated, multicast traffic begins to flow to the new client.
Path messages for the flow can reach it as well, and soft state assures that a periodic path message from the sender will eventually reach the new client.
With this path message in hand, the client can identify the flow and place its own reservations.

7. How does label distribution in MPLS assist in the creation of a RSVP reserved flows ? Describe briefly the steps involved in this process which lead to the creation of a label switched path (LSP).

Labels are bound between flows that have RSVP reservations (through the use of a FEC) and then distributed through the MPLS network.

When an LSR wants to send a RESV message for a new RSVP flow:

(i) It allocates a label from its pool of free labels

(ii) Creates an entry in its LFIB with the incoming label set to the allocated label

(iii) Sends out the RESV message containing this label to the upstream LSR.

(iv) Upon receipt of a RESV that contains this label, an LSR populates its LFIB with this label as the outgoing label

(v) It then allocates a new label to use as the incoming label and inserts that in the RESV message before sending it upstream.

(vi) As RESV messages propagate upstream, an LSP is established along the path.

8. What is meant by Per Hop Behaviour (PHB) in the context of the DiffServ approach to QOS allocation and how is it indicated ? Briefly describe the 3 main types of PHBs

DiffServ allows each node along the path to define the service that a given class will receive and this can vary from node to node along a given path, therefore DiffServ does not provide QOS end-to-end guarantees. Each of the standard PHBs is indicated by a recommended DSCP value, and each router has a table that maps the DSCP found in a packet to the PHB that will determine how that packet is treated

Default - No special treatment, equivalent to best effort.

Expedited forwarding (EF) - Packets marked EF should be forwarded with minimal delay and experience low loss.

Assured forwarding (AF) - Packets go into different priority queues where they have different drop preferences if congestion occurs

9. Briefly describe the standard approach towards congestion avoidance in TCP and state two disadvantages with this approach. Explain how Explicit Congestion Notification (ECN) overcomes these disadvantages.

Congestion avoidance in TCP assumes that packet losses in the network are an indication of congestion, and reduce their sending rates when they experience packet loss.

Disadvantages:

(i) For real time applications, the lost packet will need to be transmitted and its late arrival will cause degradation

(ii) A lost packet consumes resources up to the point it is lost, it would be preferable not to send the packet at all if it is just going to be thrown away

Router sets “congestion experienced” (CE) bit in packet header when it detects congestion, and then forward the packets rather than dropping it. The router must have some form of queue management to actively monitor congestion. When a packet with the CE bit arrives at its destination, the receiver must send a signal back to the sender that will cause the sender to reduce its sending rate.

· The token buffer can hold at most three (3) tokens, and is initially filled with two (2) tokens at time slot t = 0.

· The size of the packet queue is four (i.e. it can queue a maximum of 4 packets at any given time slot); any extra arriving packets are dropped.

· Packets that obtain available tokens in a given time slot go together on the same time slot in the output link.

Time slot	Incoming Packets
0	A B C D
1	E F
2	G
3	-
4	-
5	H I J K
6	L M N O
7	P Q
8	-
9	R S T

Time slot	Packets in queue	Tokens in bucket	Packets at output
0	A B C D	2	A B
1	C D E F	2	C D
2	E F G	2	E F
3	G	2	G
4	-	3	-
5	H I J K	3	H I J
6	K L M N	2	K L
7	M N P Q	2	M N
8	P Q	2	P Q
9	R S T	2	R S

UCEN 3133 Advanced Computer Networks - Tutorial 3 - Year 2012

2012-05-15T19:38:00.000+08:00

Tutorial 3 – MPLS Operation

1. A smaller autonomous system (AS) is defined inside the boundaries of a larger AS, and both of them employ MPLS to forward packets. A label switched path (LSP) has already been established from end-to-end between edge Label Switched Routers (LSRs) from the larger AS. This LSP tunnels through the smaller AS. In this scenario, what mechanism does MPLS provide in order to minimize routing information maintenance in the internal LSRs of the smaller AS ? Describe in detail how this mechanism works as a labelled packet is forwarded through the smaller AS.

MPLS uses a stack of labels.

When a transit packet arrives with its own label corresponding to an external LSP, the ingress LSR of the smaller AS pushes a new label onto the label stack.
This new label corresponds to an internal LSP within the smaller AS
The internal LSRs of the smaller AS switch the packet through to the egress LSR, working only on the topmost label (the new label)
At the egress LSR of the smaller AS, the new label is popped off the stack restoring original label.
The packet resumes its travel using the original external LSP for the larger AS.

2. What is the motivation behind the use of Penultimate Hop Popping in an MPLS network ? Describe briefly how it works.

It provides a form of optimization to minimize the performance penalty incurred when the egress LSR of a MPLS network has to perform two lookup operations when processing a label stack. When a packet with a stack of two labels arrives at the penultimate LSR (the LSR before the egress LSR), it pops the top stack before forwarding it onwards to the last stack.

3. Distinguish between the independent and ordered control approach to exchanging labels in the Label Distribution Protocol (LDP).

Independent control - Each LSR advertises label mappings at will. In an unsolicited mode, LSRs will generally advertise new labels whenever the IP routing information changes.

Ordered control - In this mode, all path advertisements originate at the egress router, and the label advertisement messages travel upstream to the ingress router. For advertisement on demand, a request from the ingress router triggers a chain of requests downstream to the egress router

4. Explain, with the aid of a diagram, how the liberal approach to label retention works in the LDP ? What advantage does the liberal approach offer over the conservative approach, and what is its corresponding disadvantage ?

It retains all label mappings even if they don’t correspond to an existing LSP.

Advantage: If the next hop path changes for the LSP, the given LSR may already have a new LSP ready, so it can react to the routing change almost immediately. Whereas in conservative approach, the LSR will need to request label mappings first from alternative downstream LSRs in the neighbourhood.
Disadvantage: Larger mapping table space required to keep all the labels, as well as network overhead in label exchange when the number of neighbouring LSRs is very large.

5. Explain two approaches that could be employed to address the potential problem of loops in the label distribution protocol (LDP)

· The hop count field in the label request message is incremented by all LSRs that the message passes through. If the hop count ever reaches a maximum value, a loop has occurred and the LSR sends a LDP notification message to the originator of the message.

Path vectors - Each router inserts its own LSR ID in the path vector field of the message, and if it ever finds its own ID here in a newly received message, it breaks the loop

6. Name the two situations in which a LSR in the middle of a LSP may need to return an Internet Control Message Protocol (ICMP) error message to a datagram’s source. What is the problem with using ICMP in a Virtual Private Network (VPN) deployed using MPLS, and how is this addressed by the LSR that wishes to create the ICMP message ?

Two situations:

The datagrams hop limit may run out
The packet may encounter a problem in a link between routers (link broken, or datagram too large to be fragmented and sent over link)

In a VPN, only the egress router at the boundary of the VPN is able to access the source IP address. Other intermediate routers cannot access the source IP address (which is encrypted using IPSec), and hence cannot route the appropriate ICMP message back to the source.

This is addressed by creating a ICMP message and adding the original stack label from the packet that caused the error. This ICMP datagram will follow the route of the original packet to the egress router, who can then successfully route it back to its source.

7. How might a session initialization deadlock occur during the LDP of a MPLS ? Explain how this can be overcome using the LDP hello message.

As part of LDP, two LSRs may not be able to agree on parameters during session initialization. The propose / reject cycle could then continue indefinitely, causing a deadlock. This can be overcome by having the network administrator intervene and make the passive LSR accept the proposed session. To make the active LSR propose again, the passive LSR increments the configuration sequence number in its hello messages to the active LSR.

UCEN 3133 Advanced Computer Networks - Tutorial 2 - Year 2012

2012-05-13T19:34:00.000+08:00

Tutorial 2 – MPLS Overview

1. Sketch the diagram of an Edge LSR (Label Switching Router). Identify 3 components that are important with respect to label switching at the periphery of an autonomous MPLS network, and briefly explain how they function.

(i) The Forwarding Information Base (FIB) is a standard IP forwarding table extended with labelling information. It allows labelled packets from within the MPLS core network to routed forwards as pure IP packets

(ii) Label Information Base (LIB) - holds all labels assigned by this LSR and the mappings of these labels to labels received from any neighboring LSRs, during the process of label binding exchange.

(iii) Label Forwarding Information Base (LFIB) is used during the actual forwarding of labelled packets and holds only labels that are in use currently

2. Explain how labels can be useful as a preliminary measure towards the enforcement of some form of QOS guarantee in a MPLS, making reference in your answer to Forward Equivalence Class (FEC)

Forwarding Equivalence Class (FECs) is a way of grouping incoming packets in some way so that all packets identified with a particular FEC are treated in the same manner, for example being switched over the same path (LSP). This allows some form of QOS to be enforced on the LSRs of the label switched path (LSP) that the packets flow through. Labels are associated with each particular FEC, and the FEC is established once at the entry of the IP packet into an ingress LSR.

3. Give examples of 3 items that can be used in classifying a Forward Equivalence Class (FEC)

(i) A specific source or destination IP network address

(ii) A specific class of traffic (e.g. interactive voice, streaming media) data within the packet

(iii) The particular interface on a router which the packet arrives on

4. Explain what is meant by label disposition or imposition with respect to an edge LSR.

Label imposition is the act of appending a label, or a stack of labels, to a packet in the ingress point of the MPLS domain. Label disposition is the act of removing the last label from a packet at the egress point before it is forwarded to a neighbor that is outside the MPLS domain.

5. Consider that an egress LSR in autonomous MPLS (AS 1) is communicating with its peer in another autonomous MPLS network (AS 2) using a suitable protocol (BGP for example). The process of negotiation between these peers results in a decision that exiting IP packets with a specific subnet prefix from the egress LSR in AS1 is to be routed along a specific Label Switched Path (LSP) in AS 2. Sketch an outline of how this might be accomplished using labels. What is the advantage of this approach ?

The ingress edge LSR at AS1 negotiates with the egress LSR of AS1, to append a label to all incoming packets into AS1. This label specifies that packets with a specific subnet prefix are meant to be switched immediately onwards to AS2 once they exit from AS1. The AS1 ingress LSR builds a label stack by pushing another label corresponding to an LSP that terminates at the IP address of the AS1 egress LSR. This packet with two labels is forwarded along a LSP in AS1. All the other LSRs in the LSP in AS1 only perform switching on the top most label in the stack. Finally, at the egress LSR of AS1 this label is popped leaving the bottom label – which is used to forward the packet on to the ingress router of AS2

UCEN 3133 Advanced Computer Networks - Tutorial 1

2012-04-16T22:13:00.000+08:00

1. Explain how connection oriented switching (as exemplified by technologies like ATM or MPLS) provides an advantage of speed over connectionless packet switching technologies (such as TCP/IP) ?

Connection oriented switching uses the label on a packet as an index into an internal table to forward the packets onwards. The process of indexing into a table is faster than searching a table (which is the mechanism used in routing), particularly when the indexing can be implemented in hardware

2. Describe briefly 4 underlying reasons why ATM was not adopted on a larger scale. What factor makes MPLS more attractive to a broader adoption in comparison to ATM ?

Expense: ATM switches and NIC much more expensive than Ethernet: existing Ethernet equipment in IP networks could not be reused
Connection set up latency: Since ATM is connection oriented, the packet request to set up a PVC has to pass through many switches before acknowledgment
Cell overhead: the large ATM cell header provides a big overhead
Specification of QOS requirements difficult: not all applications know beforehand the QOS that they require during a session.

MPLS was designed to build on top of the existing IP infrastructure (particularly layer 2 – Ethernet), rather than replace it completely – which makes it easier for companies with legacy IP infrastructure to migrate.

3. Explain how a Switched Virtual Circuit (SVC) established in an ATM network ?

The host requiring a connection sends a connection request to first ATM switch
This ATM switch then finds path to destination and forwards request to all switches along path
Each pair communicates with the next in sequence on path to choose matching VPI/VCI and store in respective tables.
Only if all switches agree to establishing the SVC, is successful acknowledgement provided, otherwise request denied.
The request setup SVC is done through signalling control and request messages, sent across reserved connections for control traffic

4. Briefly describe 3 advantages offered by switching across an IP infrastructure

Faster forwarding because of indexing in place of routing table lookup
Aggregated route information. IP routing table look up once when packet arrives at edge router in ISP, and packet is assigned a label for further forwarding.
Manage aggregate flows through a Service Level Agreement (SLA) easier with labels. Each label is equivalent to the Forward Equivalence Class (FEC)

5. Consider 2 hosts, X and Y, in an ATM network with 3 intermediating ATM switches, A, B and C between them. The order of connection in a newly formed PVC is X -> A -> B-> C-> Y. Given below are the switching tables for all 3 switches:

Switch C

Old VPI/VCI	Interface	New VPI/VCI
0	0	5
1	0	3
2	1	2
3	1	4
4	2	1
5	0	0

Switch B

Old VPI/VCI	Interface	New VPI/VCI
0	1	0
1	0	5
2	0	4
3	0	1
4	2	2
5	0	3

Switch A

Old VPI/VCI	Interface	New VPI/VCI
0	0	5
1	0	1
2	1	3
3	2	2
4	0	4
5	1	0

Given that the VPI/VCI leading into Y has the value of 4, what is the value of the VPI/VCI at the initial end of X ?

Answer:

From Switch C table, the old VPI/VCI resulting in 4 going into Y is 3

From Switch B table, the old VPI/VCI resulting in 3 going into Switch C is 5

From Switch A table, the original VPI/VCI resulting in 5 going into Switch B is 0

Therefore, initial end of X has VPI/VCI of 0

CCNA Challenge iPhone and iPad App FREE DOWNLOAD

2011-08-10T11:34:00.000+08:00

NetworkEquipment.net just went live with an iTunes application that is targeted to all Cisco network hardware users and is especially helpful to current and future Network Administrators, Systems Analysts, CIO's, etc.

The app, CCNA Challenge, is a fun brain teaser game that keeps the player's CCNA skill level sharp and can be used to prepare anyone for taking the CCNA exam. It was developed by a CCNA as an educational game for current CCNA's and aspiring CCNA's. CCNA Challenge can be played with no time limit to allow for beginners and those needing additional time to thoughtfully consider appropriate responses. It also has three speeds to add an additional challenge.

It has 10 different levels of 20 questions per level with all questions drawn randomly from a pool of over 2000 possible questions so the player will never get bored. This also prevents the player from memorizing the questions at any level and removing the challenge. CCNA Challenge rates the player so that an 80% successful completion rate is necessary to progress to the next level.

Those who use the timed challenge are rated at each successive level based on a combination of efficiency, quality, speed and attention. This allows any player to maximize the amount of knowledge and skill while progressing through the various levels. CCNA Challenge is available for free in the Lite version which consists of two levels of play, or in the Pro version for $1.99 which allows for an additional eight levels of play. The CCNA Challenge app also has a link to the NetworkEquipment.net website which contains a blog with valuable information about various networking issues.

There is also a surprise gift for those who successfully complete all 10 levels. NetworkEquipment.net, is a privately held company, that both buys and sells, out of channel, new and used network hardware, from Cisco Systems, Juniper Networks, Extreme Networks, Brocade Communications Systems, Redback Networks, Force10 Networks, F5 Networks and phone equipment, from Avaya and others. To find out more, please visit http://www.NetworkEquipment.net

DOWNLOAD AT http://itunes.apple.com/us/app/ccna-challenge-pro/id447047756?mt=8

Many Malaysian Government Sites Hacked

2011-06-16T22:13:00.000+08:00

Malaysia's Communications and Multimedia Commission said that 51 websites in the .gov.my domain were attacked beginning late Wednesday, and that 41 of the sites suffered various levels of disruption.

Shutdown Means Darkness For Most Government Websites
The MCMC, the country's Internet and telecommunications regulator, did not however provide information on the nature of the attacks, or the people behind it, describing them only as "unknown hackers".

However, it made references to some of the websites recovering quickly, suggesting that these sites faced a DDoS or distributed denial-of-service attack rather than a hack.

DDoS attacks can make a website inaccessible to users by swamping the website with traffic from hundreds or thousands of computers.

Such attacks are a known tactic of Anonymous, a hacker group that had threatened to attack Malaysia.

The MCMC had noticed a reduction in the levels of attack by 4 a.m. local time Thursday, it said. The attacks had little effect on Malaysian users, and most of the websites have already recovered, it said.

"We do not expect the overall recovery to these websites to take long," it said.

"The public is advised to report any information they may have regarding the identity of these hackers as the act to disrupt network services is a serious offence," it said.

Anonymous has used various online forums to threaten Malaysia with an attack in protest against the government's decision to block 10 websites that reportedly allowed the download of pirated content. Earlier this week, Anonymous invited people to join Operation Malaysia, targeting a government website from 7.30 p.m. GMT on Wednesday (3.30 a.m. Thursday, local time).

List of hacked Malaysia government website (16 June 2011, 11:26am):

http://moha.gov.my/-still cannot view
http://www.malaysia.gov.my/-still cannot view
http://www.kpdnkk.gov.my/-still cannot view
http://www.sabahtourism.com/-still cannot view
http://www.eghrmis.gov.my/-still cannot view (not sure if this because of attack)
http://penang.uitm.edu.my/-OK already
http://www.tourism.gov.my/-OK already
http://www.spr.gov.my/-OK already
http://www.bomba.gov.my/-OK already
http://www.jbiotech.gov.my/-OK already
https://ezi2care.jkm.gov.my/-Can only see Hello world from WordPress.
http://www.moe.gov.my/-OK already
http://www.cidb.gov.my/-OK already
http://www.treasury.gov.my/-OK already
http://www.kkr.gov.my/-OK already
http://www.penerangan.gov.my/-slow response (maybe because of DoS attack).
http://www.1malaysia.com.my/-slow response
http://www.parlimen.gov.my/-OK already.
http://www.rmp.gov.my/-OK already.
http://jpm.gov.my/-still cannot view
http://www.mocat.gov.my/-still cannot view.
http://www.nsc.gov.my/-OK already.
http://www.mohr.gov.my/-OK already.
http://www.kjc.gov.my/-still cannot view.

They’re also exposing 392 account details in Sabah Tourism site from over 3400 users. The data that posted online were email, addresses and passwords. It was defaced with words that include “Deface by Kambeng Merah: Credit to DarkJawa”.

CCNA Exploration 1: Network Fundamentals – Chapter 11 Exam

2011-06-11T20:44:00.000+08:00

01. Immediately after a router completes its boot sequence, the network administrator wants to check the routers configuration. From privileged EXEC mode, which of the following commands can the administrator use for this purpose? (Choose two.)

show flash
show NVRAM
show startup-config
show running-config
show version

02. Users in the network are experiencing slow response time when doing file transfers to a remote server. What command could be issued to determine if the router has experienced any input or output errors?

show running-config
show startup-config
show interfaces
show ip route
show version
show memory

03.Refer to the exhibit. A technician applies the configuration in the exhibit to a clean router. To verify the configuration, the technician issues the show running-config command in the CLI session with the router. What lines should the technician expect to see in the router output from the show running-config command?

* enable password class
  line console 0
  password ccna

* enable secret cisco
   enable password class
   line console 0
   password ccna

* enable secret 5 $1$v0/3$QyQWmJyT7zCa/yaBRasJm0
  enable password class
  line console 0
  password ccna

* enable secret cisco
  enable password 7 14141E0A1F17
  line console 0
  password 7 020507550A

* enable secret 5 $1$v0/3$QyQWmJyT7zCa/yaBRasJm0
  enable password 7 14141E0A1F17
  line console 0

04.Refer to the exhibit. A network administrator on HostA has problems accessing the FTP server. Layer three connectivity testing was successful from HostA to the S1 interface of RouterB. Which set of commands will allow the network administrator to telnet to RouterB and run debug commands?

* RouterB(config)# enable secret class
  RouterB(config)# line vty 0 4
  RouterB(config-if)# login

* RouterB(config)# enable secret class
  RouterB(config)# line vty 0 2
  RouterB(config-vty)# password cisco
  RouterB(config-vty)# login

* RouterB(config)# enable secret class
  RouterB(config)# line vty 0
  RouterB(config-line)# password cisco
  RouterB(config-line)# login

* RouterB(config)# enable secret class
  RouterB(config)# line aux 0
  RouterB(config-line)# password cisco
  RouterB(config-line)# login

* RouterB(config)# enable secret class
  RouterB(config)# line aux 0
  RouterB(config-vty)# password cisco
  RouterB(config-vty)# login

05.The connection between routers B and C has been successfully tested. However, after rebooting router C, the administrator noticed the response time between networks 10.10.3.0 and 10.10.4.0 is slower. Ping between the two routers is successful. A trace route indicates three hops from router B to router C. What else can be done to troubleshoot the problem?

Ping router B S0/1 connection from router C.
Trace the connection between router B to router C S0/1.
Issue a show ip route command in router B to verify routing is enabled.
Issue a show ip interface brief command on router C.

06. What command is used to change the default router name to Fontana?

Router# name Fontana
Router# hostname Fontana
Router(config)# name Fontana
Router(config)# hostname Fontana

07.The serial connection shown in the graphic needs to be configured. Which configuration commands must be made on the Sydney router to establish connectivity with the Melbourne site? (Choose three.)

Sydney(config-if)# ip address 201.100.53.2 255.255.255.0
Sydney(config-if)# no shutdown
Sydney(config-if)# ip address 201.100.53.1 255.255.255.224
Sydney(config-if)# clock rate 56000
Sydney(config-if)# ip host Melbourne 201.100.53.2

08.Refer to the exhibit. The output is shown for the show ip route command executed on Router A. What does the IP address 192.168.2.2 represent?

Gateway for the 192.168.1.0 network
Gateway for the 192.168.3.0 network
IP assigned to the serial port on Router A
IP assigned to the serial port on Router B

09.Refer to the exhibit. What additional command is required to allow remote access to this switch from hosts outside the local network?

NA-SW1(config-if)# no shutdown
NA-SW1(config)# enable password password
NA-SW1(config)# ip default-gateway address
NA-SW1(config-if)# description description

10. In a Cisco device, where is the IOS file stored prior to system startup?

RAM
ROM
Flash
NVRAM

11. When network services fail, which port is most often used to access a router for management purposes?

Ethernet

Console

Telnet

12. A network administrator needs to keep the user ID, password, and session contents private when establishing remote CLI connectivity with a router to manage it. Which access method should be chosen?

Telnet
Console
AUX
SSH

13. In a Cisco router, when do changes made to the running-configuration take effect?

after a system restart
as the commands are entered
when logging off the system
when the configuration is saved to the startup-configuration

14.Refer to the exhibit. Which names correctly identify the CLI mode represented by the prompt for Switch-East4#? (Choose two.)

line configuration mode
user executive mode
global configuration mode
privileged executive mode
interface configuration mode
enable mode

15. Which three terms correctly define the forms of help available within the Cisco IOS? (Choose three.)

hot keys
context-check
context-sensitive
structured check
command override
command syntax check

16. Which combination of keys would be used at the CLI prompt to interrupt a ping or traceroute process?

Ctrl-C
Ctrl-P
Ctrl-R
Ctrl-Shift-6
Ctrl-Z

17.Refer to the exhibit. What command will place the router into the correct mode to configure an appropriate interface to connect to a LAN?

UBAMA# configure terminal
UBAMA(config)# line vty 0 4
UBAMA(config)# line console 0
UBAMA(config)# interface Serial 0/0/0
UBAMA(config)# interface FastEthernet 0/1

18. On a Cisco router, which interface would be used to make the initial configuration?

Console

19.Refer to the exhibit. A student is responsible for the IP addressing, configuration and connectivity testing of the network shown in the graphic. A ping from host B to host C results in a destination unreachable but a ping from host B to host A was successful. What two reasons could account for this failure based on the graphic and partial router output for the Dallas router? (Choose two.)

The host A is turned off.
The Fa0/0 interface on Dallas is shutdown.
The LAN cable is disconnected from host B.
The S0/0/1 IP address of Dallas is improperly configured.
The Fa0/0 interface on Dallas is in a different subnet than host B.
The clock rate is missing on the serial link between Dallas and NYC.

-蓝鱼-

http://lovestoryhouse.blogspot.com

CCNA Exploration 1: Network Fundamentals – Chapter 10 Exam

2011-06-10T20:43:00.000+08:00

01.Refer to the exhibit. A student working in the lab selects a cable that is wired as shown. Which connection types can successfully be made with this cable? (Choose two.)

connecting a PC to a router’s console port
connecting two routers together via their fast ethernet ports
connecting two switches together at gigabit speeds
connecting a PC to a switch at Gigabit Ethernet speeds
connecting two devices with the same interface type at Fast Ethernet speeds

02. Which option identifies the primary interface which would be used for initial configuration of a Cisco router?

AUX interface
Ethernet interface
serial interface
console interface

03. What makes fiber preferable to copper cabling for interconnecting buildings? (Choose three.)

greater distances per cable run
lower installation cost
limited susceptibility to EMI/RFI
durable connections
greater bandwidth potential
easily terminated

04. A network administrator is required to use media in the network that can run up to 100 meters in cable length without using repeaters. The chosen media must be inexpensive and easily installed. The installation will be in a pre-existing building with limited cabling space. Which type of media would best meet these requirements?

STP
UTP
coaxial
single-mode fiber
multimode fiber

05. What does the term “attenuation” mean in data communication?

loss of signal strength as distance increases
time for a signal to reach its destination
leakage of signals from one cable pair to another
strengthening of a signal by a networking device

06. How many host addresses may be assigned on each subnetwork when using the 130.68.0.0 network address with a subnet mask of 255.255.248.0?

30
256
2046
2048
4094
4096

07. Which subnet mask would be assigned to the network address of 192.168.32.0 to provide 254 useable host addresses per subnetwork?

255.255.0.0
255.255.255.0
255.255.254.0
255.255.248.0

08. A company is planning to subnet its network for a maximum of 27 hosts. Which subnet mask would provide the needed hosts and leave the fewest unused addresses in each subnet?

255.255.255.0
255.255.255.192
255.255.255.224
255.255.255.240
255.255.255.248

09. What type of network cable is used between a terminal and a console port?

cross-over
straight-through
rollover
patch cable

10. Which device is used to create or divide broadcast domains?

hub
switch
bridge
router
repeater

11.Refer to the exhibit. What destination IP address will PC1 place in the header for a packet destined for PC2?

192.168.1.1
192.168.2.1
192.168.2.2
192.168.3.1
192.168.3.54

12.Refer to the exhibit. Based on the IP configuration shown, what would be the result of Host A and Host B attempting to communicate outside the network segment?

both host A and B would be successful
host A would be successful, host B would fail
host B would be successful, host A would fail
both Host A and B would fail

13. Which three types of connectors are commonly associated with Cisco’s V.35 serial cables? (Choose three.)

RJ 11
DB 60
Winchester 15 pin
DB 9
smart serial
RJ 45

14.Refer to the exhibit. How many subnets are required to support the network that is shown?

15. What are two common methods for setting a UTP Ethernet port to MDI or MDIX operation? (Choose two.)

cable color code association
cable selection and configuration
use of cable testers to determine pinouts
the automatic detection and negotiating of MDI/MDIX operation of the port
the enabling of the mechanism to electrically swap the transmit and receive pairs

16.Refer to the exhibit. A student is setting up a home network primarily used for extensive file transfers, streaming video, and gaming. Which network device is best suited to these types of activities in the topology shown?

wireless access point
router
hub
switch

17. Which three statements are true about the role of routers in the network? (Choose three.)

They propagate broadcasts.
They enlarge collision domains.
They segment broadcast domains.
They interconnect different network technologies.
Each router interface requires a separate network or subnet.
They maintain a common frame format between LAN and WAN interfaces.

18.Refer to the exhibit. A network administrator has decided to use packet capture software to evaluate all traffic from the student subnet on the way to the Internet. To ensure that all packets are captured, what network device should be used to connect the monitoring station to the network between R1 and R2?

hub
router
firewall appliance
wireless access point

19.Refer to the exhibit. Assume that all devices are using default settings. How many subnets are required to address the topology that is shown?

20.Refer to the exhibit. Which three statements are true about the exhibited topology? (Choose three.)

Hosts B and C are in the same subnet.
Five broadcast domains are present.
Host B is using a crossover cable to connect to the router.
Four broadcast domains are present.
Five networks are shown.
Host B is using a rollover cable to connect to the router.

21. To establish a console connection from a computer to a Cisco router, which cable wiring option would be used?

crossover cable
straight through cable
rollover cable
V.35 cable

22.Refer to the exhibit. Which three statements identify the type of cabling that would be used in the segments that are shown? (Choose three.)

Segment 1 uses backbone cabling.
Segment 1 uses a patch cable.
Segment 3 uses patch cabling.
Segment 3 uses vertical cabling.
Segment 3 uses horizontal cabling.
Segment 4 uses vertical cabling.

23.Refer to the exhibit. A network technician has been allocated the 192.168.1.0/24 private IP address range for use in the network that shown in the exhibit. Which subnet mask would be used to meet the host requirements for segment A of this internetwork?

255.255.255.128
255.255.255.192
255.255.255.224
255.255.255.240
255.255.255.248

CCNA Exploration 1: Network Fundamentals – Chapter 8 Exam

2011-06-09T20:41:00.001+08:00

01. Which OSI layer is responsible for binary transmission, cable specification, and physical aspects of network communication?

Presentation
Transport
Data Link
Physical

02. An installed fiber run can be checked for faults, integrity, and the performance of the media by using what device?

light injector
OTDR
TDR
multimeter

03. Which characteristics describe fiber optic cable? (Choose two.)

It is not affected by EMI or RFI.
Each pair of cables is wrapped in metallic foil.
It combines the technique of cancellation, shielding and twisting to protect data.
It has a maximum speed of 100 Mbps.
It is the most expensive type of LAN cabling.

04. When is a straight-through cable used in a network?

when connecting a router through the console port
when connecting one switch to another switch
when connecting a host to a switch
when connecting a router to another router

05. Refer to the exhibit. Which type of Category 5 cable is used to make an Ethernet connection between Host A and Host B?

coax cable
rollover cable
crossover cable
straight-through cable

06. Which method of signal transmission uses radio waves to carry signals?

electrical
optical
wireless
acoustic

07. In most business LANs, which connector is used with twisted-pair networking cable?

BNC
RJ-11
RJ-45
Type F

08. Which of the following is a characteristic of single-mode fiber-optic cable?

generally uses LEDs as the light source
relatively larger core with multiple light paths
less expensive than multimode
generally uses lasers as the light source

09. Which type of cable run is most often associated with fiber-optic cable?

backbone cable
horizontal cable
patch cable
work area cable

10. What are three measures of data transfer? (Choose three.)

goodput
frequency
amplitude
throughput
crosstalk
bandwidth

11. With the use of unshielded twisted-pair copper wire in a network, what causes crosstalk within the cable pairs?

the magnetic field around the adjacent pairs of wire
the use of braided wire to shield the adjacent wire pairs
the reflection of the electrical wave back from the far end of the cable
the collision caused by two nodes trying to use the media simultaneously

12. What is a primary role of the Physical layer in transmitting data on the network?

create the signals that represent the bits in each frame on to the media
provide physical addressing to the devices
determine the path packets take through the network
control data access to the media

13. In LAN installations where potential electrical hazards or electromagnetic interference may be present, what type of media is recommended for backbone cabling?

coax
fiber
Cat5e UTP
Cat6 UTP
STP

14. What is a possible effect of improperly applying a connector to a network cable?

Data will be forwarded to the wrong node.
Data transmitted through that cable may experience signal loss.
An improper signaling method will be implemented for data transmitted on that cable.
The encoding method for data sent on that cable will change to compensate for the improper connection.

15. Which fiber connector supports full duplex Ethernet?

* (Third one is the correct one)

16. What is considered a benefit of wireless as a media choice?

more host mobility
lower security risks
reduced susceptibility to interference
less impact of the surroundings on the effective coverage area

17. What characteristic of UTP cable helps reduce the effects of interference?

the metal braiding in the shielding
the reflective cladding around core
the twisting of the wires in the cable
the insulating material in the outer jacket

CCNA Exploration 1: Network Fundamentals – Chapter 7 Exam

2011-06-08T20:39:00.000+08:00

01. Which three factors should be considered when implementing a Layer 2 protocol in a network? (Choose three.)

the Layer 3 protocol selected
the geographic scope of the network
the PDU defined by the transport layer
the physical layer implementation
the number of hosts to be interconnected

02.

Refer to the exhibit. Assuming that the network in the exhibit is converged meaning the routing tables and ARP tables are complete, which MAC address will Host A place in the destination address field of Ethernet frames destined for www.server?

00-1c-41-ab-c0-00
00-0c-85-cf-65-c0
00-0c-85-cf-65-c1
00-12-3f-32-05-af

03. Which options are properties of contention-based media access for a shared media? (Choose three.)

non-deterministic
less overhead
one station transmits at a time
collisions exist
devices must wait their turn
token passing

04. What is true concerning physical and logical topologies?

The logical topology is always the same as the physical topology.
Physical topologies are concerned with how a network transfers frames.
Physical signal paths are defined by Data Link layer protocols.
Logical topologies consist of virtual connections between nodes.

05. What determines the method of media access control? (Choose two.)

network layer addressing
media sharing
application processes
logical topology
intermediary device function

06. What is true regarding media access control? (Choose three.)

Ethernet utilizes CSMA/CD
defined as placement of data frames on the media
contention-based access is also known as deterministic
802.11 utilizes CSMA/CD
Data Link layer protocols define the rules for access to different media
controlled access contains data collisions

07. Which statements describe the logical token-passing topology? (Choose two.)

Network usage is on a first come, first serve basis.
Computers are allowed to transmit data only when they possess a token.
Data from a host is received by all other hosts.
Electronic tokens are passed sequentially to each other.
Token passing networks have problems with high collision rates.

08. A network administrator has been asked to provide a graphic representation of exactly where the company network wiring and equipment are located in the building. What is this type of drawing?

logical topology
physical topology
cable path
wiring grid
access topology

09. What is the purpose of the preamble in an Ethernet frame?

is used as a padding for data
is used for timing synchronization
is used to identify the source address
is used to identify the destination address

10. What statements are true regarding addresses found at each layer of the OSI model? (Choose two.)

Layer 2 may identify devices by a physical address burned into the network card
Layer 2 identifies the applications that are communicating
Layer 3 represents a hierarchical addressing scheme
Layer 4 directs communication to the proper destination network
Layer 4 addresses are used by intermediary devices to forward data

11.

Refer to the exhibit. Which statement describes the media access control methods that are used by the networks in the exhibit?

All three networks use CSMA/CA
None of the networks require media access control.
Network 1 uses CSMA/CD and Network 3 uses CSMA/CA.
Network 1 uses CSMA/CA and Network 2 uses CSMA/CD.
Network 2 uses CSMA/CA and Network 3 uses CSMA/CD.

12.

Refer to the exhibit. How many CRC calculations will take place as traffic routes from the PC to the laptop?

13.

Refer to the exhibit. A frame is being sent from the PC to the laptop. Which source MAC and IP addresses will be included in the frame as it leaves RouterB? (Choose two.)

source MAC – PC
source MAC – S0/0 on RouterA
source MAC – Fa0/1 on RouterB
source IP – PC
source IP – S0/0 on RouterA
source IP – Fa0/1 of RouterB

14. Which sublayer of the data link layer prepares a signal to be transmitted at the physical layer?

LLC
MAC
HDLC
NIC

15. What two facts are true when a device is moved from one network or subnet to another? (Choose two.)

The Layer 2 address must be reassigned.
The default gateway address should not be changed.
The device will still operate at the same Layer 2 address.
Applications and services will need additional port numbers assigned.
The Layer 3 address must be reassigned to allow communications to the new network.

16. What is a function of the data link layer?

provides the formatting of data
provides end-to-end delivery of data between hosts
provides delivery of data between two applications
provides for the exchange data over a common local media

17. What is a characteristic of a logical point-to-point topology?

The nodes are physically connected.
The physical arrangement of the nodes is restricted.
The media access control protocol can be very simple.
The data link layer protocol used over the link requires a large frame header.

18. What is a primary purpose of encapsulating packets into frames?

provide routes across the internetwork
format the data for presentation to the user
facilitate the entry and exit of data on media
identify the services to which transported data is associated

19. What is the primary purpose of the trailer in a data link layer frame?

define the logical topology
provide media access control
support frame error detection
carry routing information for the frame

20. What are three characteristics of valid Ethernet Layer 2 addresses? (Choose three.)

They are 48 binary bits in length.
They are considered physical addresses.
They are generally represented in hexadecimal format.
They consist of four eight-bit octets of binary numbers.
They are used to determine the data path through the network.
They must be changed when an Ethernet device is added or moved within the network.

CCNA Exploration 1: Network Fundamentals – Chapter 6 Exam

2011-06-07T20:39:00.000+08:00

01.

Refer to the exhibit. Which network prefix will implement the IP addressing scheme for the LANs shown in the graphic?

02. Which IPv4 subnetted addresses represent valid host addresses? (Choose three.)

172.16.4.127 /26
172.16.4.155 /26
172.16.4.193 /26
172.16.4.95 /27
172.16.4.159 /27
172.16.4.207 /27

03. Which statements are true regarding IP addressing? (Choose two.)

NAT translates public addresses to private addresses destined for the Internet.
Only one company is allowed to use a specific private network address space.
Private addresses are blocked from public Internet by router.
Network 172.32.0.0 is part of the private address space.
IP address 127.0.0.1 can be used for a host to direct traffic to itself.

04. Which process do routers use to determine the subnet network address based upon a given IP address and subnet mask?

binary adding
hexadecimal anding
binary division
binary multiplication
binary ANDing

05.

Refer to the exhibit. Host A is connected to the LAN, but it cannot get access to any resources on the Internet. The configuration of the host is shown in the exhibit. What could be the cause of the problem?

The host subnet mask is incorrect.
The default gateway is a network address.
The default gateway is a broadcast address.
The default gateway is on a different subnet from the host.

06. What subnet mask would a network administrator assign to a network address of 172.30.1.0 if it were possible to have up to 254 hosts?

255.255.0.0
255.255.255.0
255.255.254.0
255.255.248.0

07. Which three IP addresses are private? (Choose three.)

172.168.33.1
10.35.66.70
192.168.99.5
172.18.88.90
192.33.55.89
172.35.16.5

08. Given the IP address and subnet mask of 172.16.134.64 255.255.255.224, which of the following would describe this address?

This is a useable host address.
This is a broadcast address.
This is a network address.
This is not a valid address.

09. A router interface has been assigned an IP address of 172.16.192.166 with a mask of 255.255.255.248. To which subnet does the IP address belong?

172.16.0.0
172.16.192.0
172.16.192.128
172.16.192.160
172.16.192.168
172.16.192.176

10.

Refer to the exhibit. The network administrator has assigned the internetwork of LBMISS an address range of 192.168.10.0. This address range has been subnetted using a /29 mask. In order to accommodate a new building, the technician has decided to use the fifth subnet for configuring the new network (subnet zero is the first subnet). By company policies, the router interface is always assigned the first usable host address and the workgroup server is given the last usable host address. Which configuration should be entered into the workgroup server’s properties to allow connectivity to the network?

IP address: 192.168.10.38 subnet mask: 255.255.255.240 default gateway: 192.168.10.39
IP address: 192.168.10.38 subnet mask: 255.255.255.240 default gateway: 192.168.10.33
IP address: 192.168.10.38 subnet mask: 255.255.255.248 default gateway: 192.168.10.33
IP address: 192.168.10.39 subnet mask: 255.255.255.248 default gateway: 192.168.10.31
IP address: 192.168.10.254 subnet mask: 255.255.255.0 default gateway: 192.168.10.1

11. Which of the following network devices are recommended to be assigned static IP addresses? (Choose three.)

LAN workstations
servers
network printers
routers
remote workstations
laptops

12. Which of the following are features of IPv6? (Choose three.)

larger address space
faster routing protocols
data types and classes of service
authentication and encryption
improved host naming conventions
same addressing scheme as IPv4

13. What is the primary reason for development of IPv6?

security
header format simplification
expanded addressing capabilities
addressing simplification

14. What two things will happen if a router receives an ICMP packet which has a TTL value of 1 and the destination host is several hops away? (Choose two.)

The router will discard the packet.
The router will decrement the TTL value and forward the packet to the next router on the path to the destination host.
The router will send a time exceeded message to the source host.
The router will increment the TTL value and forward the packet to the next router on the path to the destination host.
The router will send an ICMP Redirect Message to the source host.

15.

Refer to the exhibit. Why would the response shown be displayed after issuing the command ping 127.0.0.1 on a PC?

The IP settings are not properly configured on the host.
Internet Protocol is not properly installed on the host.
There is a problem at the physical or data link layer.
The default gateway device is not operating.
A router on the path to the destination host has gone down.

16. How many bits make up an IPv4 address?

17.

Refer to the exhibit. A network administrator discovers that host A is having trouble with Internet connectivity, but the server farm has full connectivity. In addition, host A has full connectivity to the server farm. What is a possible cause of this problem?

The router has an incorrect gateway.
Host A has an overlapping network address.
Host A has an incorrect default gateway configured.
Host A has an incorrect subnet mask.
NAT is required for the host A network.

18. What three facts are true about the network portion of an IPv4 address? (Choose three.)

identifies an individual device
is identical for all hosts in a broadcast domain
is altered as packet is forwarded
varies in length
is used to forward packets
uses flat addressing

19. What is a group of hosts called that have identical bit patterns in the high order bits of their addresses?

an internet
a network
an octet
a radix

20. What is the network address of the host 172.25.67.99 /23 in binary?

10101100. 00011001.01000011.00000000
10101100. 00011001.01000011.11111111
10101100. 00011001.01000010.00000000
10101100. 00011001.01000010.01100011
10101100. 00010001.01000011. 01100010
10101100. 00011001.00000000.00000000

21.

Refer to the exhibit. A network administrator has to develop an IP addressing scheme that uses the 192.168.1.0 /24 address space. The network that contains the serial link has already been addressed out of a separate range. Each network will be allocated the same number of host addresses. Which network mask will be appropriate to address the remaining networks?

255.255.255.248
255.255.255.224
255.255.255.192
255.255.255.240
255.255.255.128
255.255.255.252

CCNA Exploration 1: Network Fundamentals – Chapter 5 Exam

2011-06-06T20:38:00.000+08:00

01. In an IPv4 environment, what information is used by the router to forward data packets from one interface of a router to another?

destination network address
source network address
source MAC address
well known port destination address

02. What information is added during encapsulation at OSI Layer 3?

source and destination MAC
source and destination application protocol
source and destination port number
source and destination IP address

03. In a connectionless system, which of the following is correct?

The destination is contacted before a packet is sent.
The destination is not contacted before a packet is sent.
The destination sends an acknowledgement to the source that indicates the packet was received.
The destination sends an acknowledgement to the source that requests the next packet to be sent.

04. Which IP packet field will prevent endless loops?

type-of-service
identification
flags
time-to-live
header checksum

05. Which portion of the network layer address does a router use to forward packets?

host portion
broadcast address
network portion
gateway address

06.

Refer to the exhibit. Using the network in the exhibit, what would be the default gateway address for host A in the 192.133.219.0 network?

192.135.250.1
192.31.7.1
192.133.219.0
192.133.219.1

07. If the default gateway is configured incorrectly on the host, what is the impact on communications?

The host is unable to communicate on the local network.
The host can communicate with other hosts on the local network, but is unable to communicate with hosts on remote networks.
The host can communicate with other hosts on remote networks, but is unable to communicate with hosts on the local network.
There is no impact on communications.

08. What is the purpose of a default gateway?

physically connects a computer to a network
provides a permanent address to a computer
identifies the network to which a computer is connected
identifies the logical address of a networked computer and uniquely identifies it to the rest of the network
identifies the device that allows local network computers to communicate with devices on other networks

09. What type of routing uses information that is manually entered into the routing table?

dynamic
interior
static
standard

10. When the destination network is not listed in the routing table of a Cisco router, what are two possible actions that the router might take? (Choose two.)

The router sends an ARP request to determine the required next hop address.
The router discards the packet.
The router forwards the packet toward the next hop indicated in the ARP table.
The router forwards the packet to the interface indicated by the source address.
The router forwards the packet out the interface indicated by the default route entry.

11. What are the key factors to consider when grouping hosts into a common network? (Choose three.)

gateways
purpose
physical addressing
software version
geographic location
ownership

12. What is a component of a routing table entry?

the MAC address of the interface of the router
the destination Layer 4 port number
the destination host address
the next-hop address

13. Which intermediary devices could be used to implement security between networks? (Choose two.)

router
hub
switch
firewall
access point
bridge

14. What are three common problems with a large network? (Choose three.)

too few broadcasts
performance degradation
security issues
limited management responsibility
host identification
protocol compatibility

15.

Refer to the exhibit. All devices shown in the exhibit have factory default settings. How many broadcast domains are represented in the topology that is shown?

16. Which three statements are true about routes and their use? (Choose three.)

If no route to the destination network is found, the packet is returned to the previous router.
If the destination network is directly connected, the router forwards the packet to the destination host.
If multiple network entries exist for the destination network, the most general route is used to forward the packet.
If no route exists for the destination network and a default route is present, the packet is forwarded to the next-hop router.
If the originating host has a default gateway configured, the packet for a remote network can be forwarded using that route.
If a host does not have a route manually configured for the destination network, the host will drop the packet.

17.

Refer to the exhibit. A network administrator is troubleshooting a connectivity problem and needs to determine the address that is used to forward network packets out the network. Using the netstat -r command, the administrator would identify which address as the address to which all hosts send packets that are destined for an outside network?

10.10.10.26
127.0.0.1
10.10.10.6
10.10.10.1
224.0.0.0

18.

Refer to the exhibit. A network administrator notices that there are too many broadcasts on the network. What two steps can the network administrator take to resolve this problem? (Choose two.)

Replace S2 with a router.
Place all servers on S1.
Disable TCP/IP broadcasts.
Subnet the 192.168.0.0 /24 network.
Disable all unused interfaces on the switches.

19.

Refer to the exhibit. The network in the exhibit is fully operational. What two statements correctly describe the routing for the topology that is shown? (Choose two.)

192.168.0.2 is the next-hop address that is used by R3 to route a packet from the 10.0.0.0 network to the 172.16.0.0 network.
10.0.0.1 is the next-hop address that is used by R1 to route a packet from the 192.168.12.0 network to the 10.0.0.0 network.
192.168.0.1 is the next-hop address that is used by R1 to route a packet from the 192.168.12.0 network to the 172.16.0.0 network.
172.16.0.1 is the next-hop address that is used by R3 to route a packet from the 10.0.0.0 to the 172.16.0.0 network.
192.168.0.1 is the next-hop address that is used by R2 to route a packet from the 172.16.0.0 network to the 192.168.12.0 network.
192.168.0.2 is the next-hop address that is used by R2 to route a packet from the 172.16.0.0 network to the 192.168.12.0 network.

20. What two characteristics are commonly associated with dynamic routing protocols? (Choose two.)

require no device configuration
provide routers with up-to-date routing tables
require less processing power than static routes require
consume bandwidth to exchange route information
prevent manual configuration and maintenance of the routing table

21. What statement describes the purpose of a default route?

A host uses a default route to transfer data to another host on the same network segment.
A host uses a default route to forward data to the local switch as the next hop to all destinations.
A host uses a default route to identify the Layer 2 address of an end device on the local network.
A host uses a default route to transfer data to a host outside the local network when no other route to the destination exists.

CCNA Exploration 1: Network Fundamentals – Chapter 4 Exam

2011-06-05T20:37:00.000+08:00

01.

Based on the transport layer header shown in the diagram, which of the following statements describe the established session? (Choose two.)

This is a UDP header.
This contains a Telnet request.
This contains a TFTP data transfer.
The return packet from this remote host will have an Acknowledgement Number of 43693.
This is a TCP header.

02. With TCP/IP data encapsulation, which range of port numbers identifies all well-known applications?

0 to 255
256 to 1022
0 to 1023
1024 to 2047
49153 to 65535

03. Why are port numbers included in the TCP header of a segment?

to indicate the correct router interface that should be used to forward a segment
to identify which switch ports should receive or forward the segment
to determine which Layer 3 protocol should be used to encapsulate the data
to enable a receiving host to forward the data to the appropriate application
to allow the receiving host to assemble the packet in the proper order

04. Which OSI model layer is responsible for regulating the flow of information from source to destination, reliably and accurately?

application
presentation
session
transport
network

05.

Refer to the exhibit. Host A is using FTP to download a large file from Server 1. During the download process, Server 1 does not receive an acknowledgment from Host A for several bytes of transferred data. What action will Server 1 take as a result?

create a Layer 1 jam signal
reach a timeout and resend the data that needs to be acknowledged
send a RESET bit to the host
change the window size in the Layer 4 header

06. Why is flow control used for TCP data transfer?

to synchronize equipment speed for sent data
to synchronize and order sequence numbers so data is sent in complete numerical order
to prevent the receiver from being overwhelmed by incoming data
to synchronize window size on the server
to simplify data transfer to multiple hosts

07. Which two options represent Layer 4 addressing? (Choose two.)

identifies the destination network
identifies source and destination hosts
identifies the communicating applications
identifies multiple conversations between the hosts
identifies the devices communicating over the local media

08.

Refer to the exhibit. In line 7 of this Wireshark capture, what TCP operation is being performed?

session establishment
segment retransmit
data transfer
session disconnect

09.

Refer to the exhibit. What two pieces of information can be determined from the output that is shown? (Choose two.)

The local host is using three client sessions.
The local host is using web sessions to a remote server.
The local host is listening for TCP connections using public addresses.
The local host is using well-known port numbers to identify the source ports.
The local host is performing the three-way handshake with 192.168.1.101:1037.

10. What is dynamically selected by the source host when forwarding data?

destination logical address
source physical address
default gateway address
source port

11. What are two features of the User Datagram Protocol (UDP)? (Choose two.)

flow control
low overhead
connectionless
connection-oriented
sequence and acknowledgements

12. What mechanism is used by TCP to provide flow control as segments travel from source to destination?

sequence numbers
session establishment
window size
acknowledgments

13. Which transport layer protocol provides low overhead and would be used for applications which do not require reliable data delivery?

TCP
IP
UDP
HTTP
DNS

14. Which information is found in both the TCP and UDP header information?

sequencing
flow control
acknowledgments
source and destination port

15. Which three features allow TCP to reliably and accurately track the transmission of data from source to destination? (Choose three.)

flow control
urgent pointer
best effort delivery
session establishment
connectionless services
numbering and sequencing

16. During a TCP communication session, if the packets arrive to the destination out of order, what will happen to the original message?

The packets will not be delivered.
The packets will be retransmitted from the source.
The packets will be delivered and reassembled at the destination.
The packets will be delivered and not reassembled at the destination.

17. Which is an important characteristic of UDP?

acknowledgement of data delivery
minimal delays in data delivery
high reliability of data delivery
same order data delivery

18. After a web browser makes a request to a web server that is listening to the standard port, what will be the source port number in the TCP header of the response from the server?

13
53
80
1024
1728

19. Which event occurs during the transport layer three-way handshake?

The two applications exchange data.
TCP initializes the sequence numbers for the sessions.
UDP establishes the maximum number of bytes to be sent.
The server acknowledges the bytes of data received from the client.

20.

Refer to the exhibit. Host1 is in the process of setting up a TCP session with Host2. Host1 has sent a SYN message to begin session establishment. What happens next?

Host1 sends a segment with the ACK flag = 0, SYN flag = 0 to Host2.
Host1 sends a segment with the ACK flag = 1, SYN flag = 0 to Host2.
Host1 sends a segment with the ACK flag = 1, SYN flag = 1 to Host2.
Host2 sends a segment with the ACK flag = 0, SYN flag = 1 to Host1.
Host2 sends a segment with the ACK flag = 1, SYN flag = 0 to Host1.
Host2 sends a segment with the ACK flag = 1, SYN flag = 1 to Host1.

CCNA Exploration 1: Network Fundamentals – Chapter 3 Exam

2011-06-04T20:34:00.000+08:00

01. What application layer protocol is commonly used to support for file transfers between a client and a server?

HTML
HTTP
FTP
Telnet

02. What are two forms of application layer software? (Choose two.)

applications
dialogs
requests
services
syntax

03. A network administrator is designing a network for a new branch office of twenty-five users. What are the advantages of using a client-server model? (Choose two.)

centralized administration
does not require specialized software
security is easier to enforce
lower cost implementation
provides a single point of failure

04. What is the purpose of resource records in DNS?

temporarily holds resolved entries
used by the server to resolve names
sent by the client to during a query
passes authentication information between the server and client

05. What is the automated service that matches resource names with the required IP address?

HTTP
SSH
FQDN
DNS
Telnet
SMTP

06. What three protocols operate at the Application layer of the OSI model? (Choose three.)

ARP
DNS
PPP
SMTP
POP
ICMP

07. What are three properties of peer-to-peer applications? (Choose three.)

acts as both a client and server within the same communication
requires centralized account administration
hybrid mode includes a centralized directory of files
can be used in client-server networks
requires a direct physical connection between devices
centralized authentication is required

08. Which application layer protocols correctly match a corresponding function? (Choose two.)

DNS dynamically allocates IP addresses to hosts
HTTP transfers data from a web server to a client
POP delivers email from the client to the server email server
SMTP supports file sharing
Telnet provides a virtual connection for remote access

09. Which email components are used to forward mail between servers? (Choose two.)

MDA
IMAP
MTA
POP
SMTP
MUA

10. As compared to SSH, what is the primary disadvantage of telnet?

not widely available
does not support encryption
consumes more network bandwidth
does not support authentication

11. Which statements are correct concerning the role of the MTA in handling email? (Choose three.)

routes email to the MDA on other servers
receives email from the client’s MUA
receives email via the POP3 protocol
passes email to the MDA for final delivery
uses SMTP to route email between servers
delivers email to clients via the POP3 protocol

12. Which two protocols are used to control the transfer of web resources from a web server to a client browser? (Choose two.)

ASP
FTP
HTML
HTTP
HTTPS
IP

13. A small home network has been installed to interconnect three computers together for gaming and file sharing. What two properties represent this network type? (Choose two.)

User accounts are centralized.
Security is difficult to enforce.
Specialized operating system software is required.
File permissions are controlled by a single computer.
A computer that responds to a file sharing request is functioning as a server.

14. Which layer of the OSI model supplies services that allow user to interface with the network?

physical
session
network
presentation
application
transport

15.
Refer to the exhibit. What is the destination port for the communication that is represented on line 5?

80
1261
15533
3912
65520

16. What are two characteristics of peer-to-peer networks? (Choose two.)

scalable
one way data flow
decentralized resources
centralized user accounts
resource sharing without a dedicated server

17. What application layer protocol describes the services that are used for file sharing in Microsoft networks?

DHCP
DNS
SMB
SMTP
Telnet

18. What are two characteristics of clients in data networks? (Choose two.)

use daemons
initiate data exchanges
are repositories of data
may upload data to servers
listen for requests from servers

19. What is the role of the OSI application layer?

provides segmentation of data
provides encryption and conversion of data
provides the interface between the applications on either end of the network
provides control of all the data flowing between the source and destination devices

20. How does the application layer on a server usually process multiple client request for services?

ceases all connections to the service
denies multiple connections to a single daemon
suspends the current connection to allow the new connection
uses support from lower layer functions to distinguish between connections to the service

CCNA Exploration 1: Network Fundamentals – Chapter 2 Exam

2011-06-02T20:32:00.000+08:00

01. Which statements correctly identify the role of intermediary devices in the network? (Choose three.)

determine pathways for data
initiate data communications
retime and retransmit data signals
originate the flow of data
manage data flows
final termination point for data flow

02. Select the statements that are correct concerning network protocols. (Choose three.)

define the structure of layer specific PDU’s
dictate how to accomplish layer functions
outline the functions necessary for communications between layers
limit the need for hardware compatibility
require layer dependent encapsulations
eliminate standardization among vendors

03. What are two functions of encapsulation? (Choose two.)

tracks delay between end devices
enables consistent network paths for communication
allows modification of the original data before transmission
identifies pieces of data as part of the same communication
ensures that data pieces can be directed to the correct receiving end device

04. What is a primary function of the trailer information added by the data link layer encapsulation?

supports error detection
ensures ordered arrival of data
provides delivery to correct destination
identifies the devices on the local network
assists intermediary devices with processing and path selection

05. Which two layers of the OSI model have the same functions as the TCP/IP model Network Access Layer? (Choose two.)

Network
Transport
Physical
Data Link
Session

06. What is a PDU?

corruption of a frame during transmission
data reassembled at the destination
retransmitted packets due to lost communication
a layer specific encapsulation

07. Which characteristic correctly refers to end devices in a network?

manage data flows
originate data flow
retime and retransmit data signals
determine pathways for data

08.

Refer to the exhibit. “Cell A” at IP address 10.0.0.34 has established an IP session with “IP Phone 1″ at IP address 172.16.1.103. Based upon the graphic, which device type best describes the function of wireless device “Cell A?”

the destination device
an end device
an intermediate device
a media device

09.

Refer to the exhibit. Which three labels correctly identify the network types for the network segments that are shown? (Choose three.)

Network A — WAN
Network B — WAN
Network C — LAN
Network B — MAN
Network C — WAN
Network A – LAN

10. Which three statements best describe a Local Area Network (LAN)? (Choose three.)

A LAN is usually in a single geographical area.
The network is administered by a single organization.
The connection between segments in the LAN is usually through a leased connection.
The security and access control of the network are controlled by a service provider.
A LAN provides network services and access to applications for users within a common organization.
Each end of the network is generally connected to a Telecommunication Service Provider (TSP).

11.

Refer to the exhibit. Which networking term describes the data interleaving process represented in the graphic?

piping
PDU
streaming
multiplexing
encapsulation

12. What is the primary purpose of Layer 4 port assignment?

to identify devices on the local media
to identify the hops between source and destination
to identify to the intermediary devices the best path through the network
to identify the source and destination end devices that are communicating
to identify the processes or services that are communicating within the end devices

13. What device is considered an intermediary device?

file server
IP phone
laptop
printer
switch

14.

Refer to the exhibit. Which term correctly identifies the device type that is included in the area B?

source
end
transfer
intermediary

15.

Refer to the exhibit. What type of network is shown?

WAN
MAN
LAN
WLAN

16. Which layer encapsulates the segment into packets?

physical
data link
network
transport

17. What can be identified by examining the network layer header?

the destination device on the local media
the destination host address
the bits that will be transferred over the media
the source application or process creating the data

18.

Refer to the exhibit. Which set of devices contains only end devices?

A, C, D
B, E, G, H
C, D, G, H, I, J
D, E, F, H, I, J
E, F, H, I, J

19. During the encapsulation process, what occurs at the data link layer?

No address is added.
The logical address is added.
The physical address is added.
The process port number is added.

20. What is the purpose of the TCP/IP Network Access layer?

path determination and packet switching
data presentation
reliability, flow control, and error detection
network media control
the division of segments into packets

21. What is the proper order of the layers of the OSI model from the highest layer to the lowest layer?

physical, network, application, data link, presentation, session, transport
application, physical, session, transport, network, data link, presentation
application, presentation, physical, session, data link, transport, network
application, presentation, session, transport, network, data link, physical
presentation, data link, session, transport, network, physical, application

Is that possible to use other streamyx account?

2011-05-20T12:36:00.000+08:00

Yes. Indeed.

For example, if your streamyx account is only basic 512K, but you got no money to upgrade to 1Mbps to watch youtube without buffering, therefore you can try out this trick how to hack other people streamyx account and use at your own place.

Disclaimer: Use this trick at your own risk !!

before year 2009, most of the streamyx customer was given default password as tmnet123. Therefore using this exploit, we can easily get the others streamyx account, all we need to do is try our luck to get the streamyx account username.

Please go to https://tmbill.tm.net.my/SelfCare/Maintenance/selfcareLogin.jsp to enter the username and password. If error as above appear, that means you might enter the wrong username or password. Try another account instead.

Once you enter the correct password and username, the message as picture above will shown. That's mean the account can be use at your own place d ! However we can only check out the internet speed only when we are successfully connect using the username and password.

Once you get the correct password and username, just log in to your modem/router and modify the connection setting. Each router may have different configuration, please refer to the respective user manual of your router/modem. Here we are using the free modem given by the streamyx as example.

If you wondering when you are using other people's streamyx account, will the people disconnected or their internet speed will be slowed down? The answer is they won't be disconnected because their account can be logged in by many users at the same time. Yes, their internet speed will be slow down, because you are using his account and thus you are sharing speed with him, so please behave yourself, DO NOT open ppstream when you are using other's people account because ppstream can eat up the 90% speed!!! Imagine u are stealing his account and you are greedy use up the 90% speed for the ppstream, his got 10% internet speed only, he pay RM88 every month to get 10% speed only? do you feel guilty? Haha. - quoted from http://ye5.blogspot.com/2010/12/hack-streamyx-account.html

But the question is how can you get many username to test it out?
The answer is simple. Use google to get it !!
Try search on the google using this string - "contact us intext:@streamyx.com", and you can possibly get million of streamyx account username. =)

CCNA netowork fundamentals Final Exam Answers 2011

2011-03-28T23:07:00.001+08:00

1. Due to a security violation, the router passwords must be changed. What information can be learned from the following configuration entries? (Choose two.)
Router(config)# line vty 0 3
Router(config-line)# password c13c0
Router(config-line)# login

The entries specify three Telnet lines for remote access.

The entries specify four Telnet lines for remote access.

The entries set the console and Telnet password to "c13c0".

Telnet access will be denied because the Telnet configuration is incomplete.

Access will be permitted for Telnet using "c13c0" as the password.

2. Which two actions could be taken by a router if a specific match is not made to a route in the routing table? (Choose two.)

The packet will be discarded.

The packet will be sent back to the source.

The packet will be flooded out all interfaces.

Neighboring routers are polled to find the best path.

The packet will be forwarded to a default route if one is present.

3.
Refer to the exhibit. The network administrator remotely accesses the CLI of RouterB from PC1 using a secure connection. Which statement is true about this connection?

The Telnet server process is running on PC1.

Only the exchange of the Telnet username and password is encrypted.

The GET request is sent to RouterA to retrieve data.

The SSH service is used to connect PC1 to RouterB.

4.

Refer to the exhibit. What three statements are true about the IP configuration that is shown? (Choose three.)

The prefix of the subnet mask is /26.

The network on which this computer resides can have 30 hosts.

The computer is unable to communicate outside of the local network.

The address that is assigned to the computer represents private addressing.

The IP address that is assigned to the computer is routable on the Internet.

The IP address that is assigned as the default gateway is valid for this host.

5. What information can be gathered by using the command netstat?

the default gateway

the routing protocol

active TCP connections

the locally configured subnet mask

6.

Refer to the exhibit. The nslookup command that is shown was issued on a Windows PC host. What does the 10.32.5.74 address represent?

the IP address of the host

the default gateway for the host

the primary DNS server for the host

the home page address for the host

7.

Refer to the exhibit. A network administrator remotely accesses the CLI of RouterB from PC1 using Telnet. Which statement is true about this connection?

The data is automatically encrypted.

A Telnet server process is running on PC1.

The connection is made through a VTY session on the router.

A GET request was sent to RouterB to retrieve data during this session.

8. Which three addresses are private IP addresses? (Choose three.)

10.0.0.1

46.1.1.88

172.31.31.10

172.32.16.10

192.168.8.8

9.

Refer to the exhibit. Host C is able to ping 127.0.0.1 successfully, but is unable to communicate with hosts A and B in the organization. What is the likely cause of the problem?

Hosts A and B are not on the same subnet as host C.

The IP addresses on the router serial interfaces are wrong.

The subnet mask on host C is improperly configured.

The FastEthernet interface fa0/0 of router 1 is wrongly configured.

10. Which OSI layer addressing is required to route packets between two networks?

Layer 1

Layer 2

Layer 3

Layer 4

11. What is the effect of using the Router# copy running-config startup-config command on a router?

The contents of ROM will change.

The contents of RAM will change.

The contents of NVRAM will change.

The contents of flash will change.

12. A PC can not connect to any remote websites, ping its default gateway, or ping a printer that is functioning properly on the local network segment. Which action will verify that the TCP/IP stack is functioning correctly on this PC?

Use the ipconfig /all command at the host’s command prompt.

Use the ping 127.0.0.1 command at the command prompt.

Use the traceroute command at the command prompt to identify any failures on the path to the gateway.

Use FTP to check for connectivity to remote sites.

Download a troubleshooting tool from the PC manufacturer’s website.

13. Which subnet mask will allow 2040 hosts per subnet on the IP network 10.0.0.0?

255.255.0.0

255.255.254.0

255.255.252.0

255.255.248.0

255.255.240.0

255.255.255.128

14.

Refer to the exhibit. When computer A sends a frame to computer D, what computers receive the frame?

only computer D

only computer A and computer D

only computer B, computer C, and computer D

all computers

15.

Refer to the exhibit. While configuring a network, a technician wired each end of a Category 5e cable as shown. Which two statements are true about this setup? (Choose two.)

The cable is suitable for connecting a switch to a router Ethernet port.

The cable is suitable for connecting dissimilar types of devices.

The cable is unusable and must be rewired.

The cable is terminated in a way that the transmit pin is wired to the receive pin.

The cable simulates a point-to-point WAN link.

16.

Refer to the exhibit. Which layered network model is shown in the diagram?

Cisco

IETF

OSI

TCP/IP

17. An administrator makes changes to the default configuration of a router and saves them to NVRAM. After testing, it is discovered that the configurations did not have the desired effect and must be removed. What steps must be taken to remove the changes and return the router to the default configuration?

Reboot the router.

Use no version of the commands that are issued.

Issue the erase startup-config command, and then reboot the router.

Issue the erase running-config command, and then reboot the router.

18.

Refer to the exhibit. Host A and B are unable to communicate with each other. What is the reason for this?

Host A is assigned a network address.

Host B is assigned a multicast address.

Host A and host B belong to different networks.

The gateway addresses are network addresses.

19.
Refer to the exhibit. A network technician has made several changes to R1 since the configuration has last been saved. The modified configuration did not produce the desired changes. The technician wants to store a backup copy of the saved configuration on a TFTP server before reloading. Which action will cause the unmodified data to be saved on the TFTP server?

20. What can the user do from the command prompt, Router(config-line)# ?

Configure one of the network interfaces.

Configure one of the physical or virtual lines.

Verify the running configuration on the device.

Configure the parameters for one of the routing protocols.

21.

Refer to the exhibit. A PC is connected to a network. Which action will verify that the PC can communicate with its default gateway?

Use the ping 127.0.0.1 command.

Use the ipconfig command.

Use the ipconfig/all command.

Use the ping 10.0.0.254 command.

22.

Refer to the exhibit. The serial interface of the router was configured with the use of the commands that are shown. The router cannot ping the router that is directly connected to interface serial 0/0/0. What should the network technician do to solve this problem?

Configure the description at interface serial 0/0/0.

Configure an IP address on interface serial 0/0/0.

Remove the no shutdown command at interface serial 0/0/0

Reboot the router.

23. A technician is asked to secure the privileged EXEC mode of a switch by requiring a password. Which type of password would require this login and be considered the most secure?

console

enable

enable secret

VTY

24. What are two purposes for configuring a banner on a router? (Choose two.)

to announce system downtime

to prevent unauthorized access to the router

to provide a description of interface connections

to assist in legal prosecution for unauthorized access

to provide a welcome message to users who access the router

25.

Refer to the exhibit. A PC is communicating with another PC on a remote network. The two networks are connected by three routers. Which action will help to identify the path between the hosts?

Use the ipconfig command at the host.

Use the ipconfig/all command at the destination.

Use the tracert command at the host.

Use the ping command at the destination.

26.

Refer to the exhibit. Which list refers only to end devices?

D,E,F,G

A,H,B,C

A,D,E,F

A,D,E,G

27. When must a router serial interface be configured with the clock rate command?

when the interface is functioning as a DTE device

when the interface timers have been cleared

when the connected DTE device is shut down

when the interface is functioning as a DCE device

28. Which table accurately associates the RFC 1918 private IP addresses with the correct network mask?
Answer No. 1

29.

Refer to the exhibit. Which two layers of the OSI model describe the same functions as the transport and internet layers of the TCP/IP model? (Choose two.)

application layer

presentation layer

session layer

transport layer

network layer

data link layer

physical layer

30. What happens when a host station receives a frame that contains its own MAC address in the destination field?

The Layer 2 information is removed and the frame is pushed up to Layer 3.

The host station will copy the information to its buffers and send it back out.

The frame originated from the host and will be ignored.

The Layer 3 information is added to the frame.

31.

Refer to the exhibit. Host A is configured with the correct IP address for the default gateway of the router R1 FastEthernet0/1 interface. How will a packet that is sent from host A to host B be handled by the devices on the network?

R1 will drop the packet because R1 does not have a specific route in its routing table to the 10.1.1.0/24 network.

R1 will forward the packet to its default gateway, the next hop router R2. R2 will forward the packet to the directly connected network 10.1.1.0/24.

R1 will forward the packet to its default gateway, the next hop router R2. R2 will drop the packet because it does not have a default route to network 10.1.1.0/24.

R1 will forward the packet to its default gateway, the next hop router R2. R2 will drop the packet because it does not have a route that is learned by a routing protocol to network 10.1.1.0/24.

32. What type of network is maintained if a server takes no dedicated role in the network?

mainframe

client/server

peer-to-peer

centralized

33. In a network design project, a network designer needs to select a device to provide collision free connections to 40 hosts on the LAN. Which device should be selected?

hub

router

switch

firewall

34. Which TCP/IP model layer creates additional overhead on network resources due to acknowledgments, tracking, and retransmission of data?

internet

transport

application

network access

35. How many host addresses may be assigned when using the 128.107.0.0 network address with a subnet mask of 255.255.248.0?

30

256

2046

2048

4094

4096

36. Which service is used when the nslookup command is issued on a computer?

FTP

DNS

DHCP

Telnet

37. Which process provides the means to send and receive data when running multiple applications at the same time on a computer?

interleaving

sequencing

segmentation

acknowledgement

38. Which three IPv4 addresses represent valid host addresses for a subnet? (Choose three.)

10.1.12.79/28

10.1.12.113/28

10.1.12.32/28

10.1.11.5/27

10.1.11.97/27

10.1.11.128/27

39. What is the consequence of issuing the erase startup-config command in privileged EXEC mode on a Cisco router?

Data stored in RAM will be removed.

Data stored in NVRAM will be erased.

Information in flash memory will be removed.

Flags in the configuration register will be set to 0.

Both the startup-config and the running-config will be erased.

40.

Refer to the exhibit. A network technician is trying to determine the correct IP address configuration for Host A. What is a valid configuration for Host A?

IP address: 192.168.100.19; Subnet Mask: 255.255.255.248; Default Gateway: 192.16.1.2

IP address: 192.168.100.20; Subnet Mask: 255.255.255.240; Default Gateway: 192.168.100.17

IP address: 192.168.100.21; Subnet Mask: 255.255.255.248; Default Gateway: 192.168.100.18

IP address: 192.168.100.22; Subnet Mask: 255.255.255.240; Default Gateway: 10.1.1.5

IP address: 192.168.100.30; Subnet Mask: 255.255.255.240; Default Gateway: 192.168.1.1

IP address: 192.168.100.31; Subnet Mask: 255.255.255.240; Default Gateway: 192.168.100.18

41. What is the Cisco IOS?

system software for Cisco devices

Read Only Memory in Cisco devices

non-volatile storage for device configurations

an initial operating system that is used for boot functions

42. Which router configuration mode will require user authentication if an administrator issues the enable secret command?

user executive mode

privileged executive mode

global configuration mode

service specific configuration mode

43. Which command or commands will require authentication to access the privileged exec mode?

RTRA(config)# enable secret cisco
RTRA(config)# service password encryption

RTRA(config)# line con 0
RTRA(config-line)# login
RTRA(config-line)# password cisco

RTRA(config)# line vty 0 4
RTRA(config-line)# login
RTRA(config-line)# password cisco

44. A routing issue has occurred in your internetwork. Which of the following type of devices should be examined to isolate this error?

access point

host

hub

router

switch

45. Which statement is true about Layer 3 addresses?

They are physical addresses.

They are used in routing decisions.

They are only used on local networks.

They are altered each time a packet crosses a router.

46.
Refer to the exhibit. An administrator on PC1 wants to view some HTML code from a web page housed on the web server. Which client application will allow this request to be started?

47. Which OSI layer does IP rely on to determine whether packets have been lost and to request retransmission?

application

presentation

session

transport

48.

Refer to the exhibit. PC1 is unable to access PC2. To troubleshoot this problem, the technician needs to confirm that the next hop interface is operational. Which default gateway address should the technician ping from PC1 to confirm this?

10.0.0.254

192.168.0.249

192.168.0.250

10.0.1.254

49. An administrator is in the middle of entering a lengthy command when suddenly output from the IOS appears stating that an interface has gone down and then up again. Consequently, the command that the administrator was typing is no longer legible on the terminal. What CLI keystrokes can be entered to return to the line that the administrator was typing?

Ctrl-D

Ctrl-K

Ctrl-R

Ctrl-Z

50. Which option represents a point-to-point logical topology diagram?

Answer No. 4

51. Which physical component is used to access and perform the initial configuration on a new unconfigured router?

Answer No. 2

52. Which option shows how a router will route packets to a remote network?

Answer No. 4

Subnet Calculator for CCNA Exam

2011-02-10T23:06:00.000+08:00

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