A Networking Media

Infrastructure Considerations for Cloud Computing

2012-02-13T06:51:00.000-08:00

Introduction

As the cloud computing trend continues to gain momentum, it is likely that you will eventually consider outsourcing some of your IT operations to a cloud service provider. Before you do however, it is important to realize that the cloud comes with an entirely new set of challenges that you may not experience with a traditional on-premise datacenter. Since some of these challenges revolve around your network infrastructure, I wanted to take the opportunity to talk about how making use of cloud services may impact your network infrastructure.

Service Level Agreements

Most of the larger organizations impose Service Level Agreements (SLAs) on their IT staff for mission critical applications. For example an organization may have an SLA that requires E-mail to be available 99.999% of the time. This so called “five nines of availability” means that the service is only permitted to be unavailable for a maximum of five minutes per year.

My point is that if you are bound by a strict SLA for your mission critical applications, then it would not be in your best interest to outsource those applications to the cloud. The reason is simple. No cloud service provider can guarantee that your SLA will be met.

Don’t get me wrong. There are some cloud service providers that will agree to be bound by an SLA. Ultimately though, the chances that the provider will actually be able to adhere to the SLA are unrealistic. After all, your organization will be connecting to the service provider over the Internet. Neither you, the cloud service provider, or your ISP controls the entire Internet. Even if a cloud service provider is able to achieve 100% availability for a hosted application, an Internet failure could render the application inaccessible. If you read the fine print on the cloud provider’s SLA, it will most likely say that the cloud provider is not responsible for Internet outages.

Internet Redundancy

In the previous section, I explained how an Internet failure could render a hosted application or service inaccessible. It is currently impossible to completely avoid Internet failures, but you can sometimes use redundancy as a means of reducing the chances of an Internet related outage.

Of course simply having multiple Internet connections alone isn’t enough. The key to achieving effective redundancy is to acquire Internet service from multiple providers. Suppose for example that you had two separate broadband connections from the same Internet provider. If that provider experienced an outage then the outage would most likely affect both of your Internet connections, which would completely defeat the purpose of having redundant Internet connections.

In some cases it may be impossible to get Internet access from multiple providers. In those types of situations you must consider whether or not you should outsource anything to the cloud. For example, I live in a rural area that is serviced by a single “mom and pop” ISP who has a monopoly on the entire area. I couldn’t get service from a second provider even if I wanted to. Although I could get redundant connections from my current ISP, my ISP has an outage about once a week. As such, I would have to be out of my mind to outsource anything important to the cloud.

Admittedly, the biggest thing stopping me from using the cloud is that my ISP isn’t very reliable. But what if you are in a situation in which your ISP is reliable, but you can’t get service from a secondary ISP?

In a situation like that redundancy may still be beneficial even if you can only get service from a single ISP. If you have redundant Internet connections from a single service provider, those connections will not protect you in the event that your ISP has an outage. It will however, help to protect you against a hardware failure. For example, if an Internet router on your network were to fail, network hosts would still be able to reach the Internet though the redundant connection.

Latency

Another factor that you will have to take into account when you are considering whether or not to outsource services to the cloud is the inherent (and unpredictable) latency that comes with using a service over the Internet.

Lately, a lot of organizations have been using cloud storage. Doing so provides them with an unlimited, on demand storage pool. While there is no denying the benefits that cloud storage can provide, it is also worth noting that cloud storage does not currently provide the same level of performance that is available through on-premise storage solutions. Furthermore, because the storage pool is Internet based, the latency is somewhat unpredictable.

To give you a better idea of what I mean, consider my own situation. I work out of my home and most of the time my Internet connection performs fairly well. However, in the late afternoon I always notice my Internet connection getting slower as my neighbors start getting home from work. Sometimes the performance decreases to the point that my connection is borderline unusable.

Granted, I work from my home, but the same problem can occur in a corporate environment. Factors such as what the users are doing at a given moment and your ISPs overall capacity can lead to fluctuations in Internet performance, and these fluctuations can translate directly to latency if you are connected to a cloud storage pool.

Client Side Software

One last infrastructure requirement that I want to mention is client side software. If you are only using the cloud for Infrastructure as a Service (IAAS) as would be the case with cloud storage then the client software isn’t really an issue. However, if you are actually hosting applications in the cloud then the software that the clients use to interface with those applications needs to be reliable.

For example, I know someone who decided to use Microsoft Office Web App rather than having the expense of licensing Microsoft Office 2010 on all of their PCs. In case you are not familiar with Office Web App, it is a collection of free, Web-based versions of the Microsoft Office applications. These applications are designed to be accessible through a Web browser.

To make a long story short, the person in question ended up visiting a malicious Web site that used a virus to disable Internet Explorer. This caused them to not only lose access to the Internet, but also to the basic productivity applications that they use every day.

Even though this event didn’t occur within a corporate environment it very well could have. Not all cloud applications are browser based, but some are. Regardless of whether a cloud application is browser based or not though, it is critical that you take measures to preserve the integrity of whatever software the client computers use to access the hosted application.

Conclusion

In this article I have explained that although there are advantages to using cloud services, hosted services present a set of challenges that are often different from what one might experience in an on-premise deployment. As such, it is important to anticipate as many of these challenges as possible and to plan accordingly before you begin outsourcing resources to the cloud.

LVM In Linux

2011-05-08T01:07:00.000-07:00

LVM

For easier hard disk storage management, you can set up your system to use the Logical Volume Manager (LVM), creating LVM partitions that are organized into logical volumes to which free space is automatically allocated. Logical volumes provide a more flexible and powerful way of dealing with disk storage, organizing physical partitions into logical volumes in which you can easily manage disk space. Disk storage for a logical volume is treated as one pool of memory, though the volume may in fact contain several hard disk partitions spread across different hard disks. Adding a new LVM partition merely increases the pool of storage accessible to the entire system.

Using the LVM Commands :-

lvdisplay :- Display detailed information about logical volumes
lvcreate :- Create logical volumes
lvrename :- Rename a logical volume
lvextend :- Extend the size of a logical volume
lvreduce :-Reduce the size of a logical volume
lvremove :-Remove logical volumes
pvdisplay :- Display detailed information about LVM physical partition
pvcreate :-Create LVM physical partitions
pvremove :-Delete LVM physical partitions
vgdisplay :-Display detailed information about volume groups
vgreduce :-Remove physical partitions from a volume group
vgremove :-Delete a volume group
vgextend :-command adds a new partition to a logical group.

Process to create LVM

Change the partition name and no only according to your system . Remain follow the same process without any change to create lvm .
# fdisk /dev/sda
N
Press Enter
+10G
N
Press Enter
+10G
T
6 (Declare Partition No.)
8e
T
7 (Declare Partition No.)
8e
W
# partprobe /dev/sda
# pvcreate /dev/sda{6,7}
# vgcreate vg0 /dev/sda{6,7}
# lvcreate –L 5G –n /dev/vg0/a
# lvcreate –L 5G –n /dev/vg0/b
# mkfs.ext4 /dev/vg0/a
# mkfs.ext4 /dev/vg0/b
# mkdir /lvm;mkdir /lvm1;mkdir /lvm/lvm2
# mount /dev/vg0/a /lvm/lvm1
# mount /dev/vg0/b /lvm/lvm2
# vi /etc/fstab
/dev/vg0/a /lvm/lvm1 ext4 defaults 0 0
/dev/vg0/b /lvm/lvm2 ext4 defaults 0 0
# lvextend -L +5G /dev/vg0/a
# lvdisplay
# df –h
# resize2fs /dev/vg0/a 15G

NFS Server in Linux

2010-12-10T22:07:00.000-08:00

NFS
NFS -> NFS stand for Network File Sharing
Using NFS you can share file on Network.NFS server allow us to share file on client side and vice-versa.
Using NFS server we can easily access any file and directory on client side.

Note -> Disabled Firewall

Note -> For NFS rpm you must need a rhel 5 DVD OR Yum configure
On your system OR an active internet connection to download
NFS rpm.
If Yum is configure on your system then login as a
Root and type,
< Yum -y install nfs* >
If you have a rhel 5 DVD then mount the DVD on any
Directory. For e.g., I mount a DVD on /mnt directory. Now login
As a root and type,
< rpm -ivh /mnt/Server/nfs* >

Now NFS package is installed on your system.

NFS works on Port number 2049/tcp -- To check Port number file is "/etc/services"
---------------------------------------------------------------------------
Server Side Configuration
On Server Side the configuration file is
< /etc/exports >
Open the /etc/exports file in any Linux editor. I suggest you open it in
VIM.
VI /etc/exports
File is blank. Now write in the file you want to share on the network for
End-Users.
For eg. I am sharing a /var/ftp/pub directory and /home directory. Enter the
these lines in /etc/exports file.

/var/ftp/pub *(ro,sync)
/home 10.10.1.20(ro,sync)

Now save & exit from file.
------------------------------------------------------------------------------------------
Here, in the /etc/exports file we write the share directory /var/ftp/pub
And in the front of we write {*(ro, sync} this mean that,

Asterisk (*) mean that you can share the /var/ftp/pub directory on all the
PC connected in the same network.

(ro) means that you have read only permission on /var/ftp/pub. You can change
{ro} to {rw).{rw} mean that you have read and write permission on
/var/ftp/pub/ directory.

(sync) stand for synchronization mean that accuracy in time to matching data.
If you want share a directory on a particular IP address then write the IP
of particular machine corresponding to the share directory.For eg
/home 10.10.1.20(ro,sync)
-----------------------------------------------------------------------------------------
After, configure the /etc/exports file restart the NFS services
service portmap restart
service nfs restart
PORTMAP -> The portmap service can be used with TCP wrappers' hosts access files (/etc/hosts.allow and /etc/hosts.deny) to control which remote systems are permitted to use RPC-based services on the server.
If you want to permanent restart NFS services during next reboot Use
Chkconfig portmap on
Chkconfig nfs on
--------------------------------------------------------------------------------------------
Now, if you want to know what you are sharing on server side, you can see it in two ways.
1. Open the /etc/exports file
2. Showmount -e 10.10.10.254 here 10.10.10.254 is server ip address.
--------------------------------------------------------------------------------------------
On Clint Side
On client side if you want to know that what is sharing from server side
login as root and type
showmount -e 10.10.10.254 server ip address result is look like this
/var/ftp/pub *(ro,sync)
/home 10.10.10.20(ro,sync)

If server gives you write permission on any share directory the mount the directory and you can
edit it. For eg
mount 10.10.10.254:/var/ftp/pub /mnt
ls /mnt
-----------------------------------------------------------------------------------------------

SAMBA SERVER IN LINUX

2010-11-22T19:30:00.000-08:00

SAMBA SERVER
Samba Server -> It is basically used for sharing file and directory on windows and Linux machine. Using it you can share printers, files and directories on window machine and Linux machine.

Note -> Disabled Firewall

Note -> Before configuring the samba server first install the samba rpm package from using YUM or using rhel 5 DVD.

Using Yum -> yum -y install samba*

------------------------------------------------------------------------------
On Server Side

After installing of samba rpm, login as root and open the samba configuration file in editing mode. The configuration file is

vi /etc/samba/smb.conf

In /etc/samba/smb.conf file go to the line number 80 and edit it like that

host allow = 127. 192.168.1

Uncomment the line and leave it.

Now go to end of file and add these lines

[Test] # Here [Test] is shared filename of directory
comment # any thing you like
path=/home/linux # Here path is your shared directory
validuser=Michal # Michal is a user name through which you can access shared
directory on linux machine.
read list=Michal # Permission for reading directory for user Michal
write list=Michal # Permission for writing share director for user

Save & Exit.

Now add a user as you define in /etc/samba/smb.conf configuration file. Here I use Michal

useradd michal
smbpasswd -a michal

Set user password.Remeber here I use "smbpasswd" not "passwd" to set password for Michal.Becaue samba server has its own file to save user passwd.Samba server retrieved the passwd information from smbpasswd file.

And on linux machine you have to must a user password to access shared directory using samba. Without it you can’t login.

----------------------------------------------------------------------------
Here I suggest you add user before configuring the /etc/samba/smb.conf file.
-----------------------------------------------------------------------------

*****************************************************************************

On client Side

To download file

smbclint -L //192.168.1.254 /test -U michal

mget filname -------> to download

mput filename -------> to upload

On Window Machine

Open--> run and the server ip address

\\192.168.1.254 press enter.

You can see only Share file name not the shared directory name.

***************************************************************************

Toughest Interview Question

2010-05-15T05:42:00.000-07:00

Question 1 Tell me about yourself.

TRAPS: Beware, about 80% of all interviews begin with this “innocent” question. Many candidates, unprepared for the question, skewer themselves by rambling, recapping , their life story, delving into ancient work history or personal matters.
BEST ANSWER: Start with the present and tell why you are well qualified for the position. Remember that the key to all successful interviewing is to match your qualifications to what the interviewer is looking for. In other words you must sell what the buyer is buying. This is the single most important strategy in job hunting.
So, before you answer this or any question it's imperative that you try to uncover your interviewer's greatest need, want, problem or goal.
To do so, make you take these two steps:
1. Do all the homework you can before the interview to uncover this person's wants and needs (not the generalized needs of the industry or company)
2. As early as you can in the interview, ask for a more complete description of what the position entails. You might say: “I have a number of accomplishments I'd like to tell you about, but I want to make the best use of our time together and talk directly to your needs. To help me do, that, could you tell me more about the most important priorities of this position? All I know is what I (heard from the recruiter, read in the classified ad, etc.)”
Then, ALWAYS follow-up with a second and possibly, third question, to draw out his needs even more. Surprisingly, it's usually this second or third question that unearths what the interviewer is most looking for.

You might ask simply, "And in addition to that?..." or, "Is there anything else you see as essential to success in this position?:
This process will not feel easy or natural at first, because it is easier simply to answer questions, but only if you uncover the employer's wants and needs will your answers make the most sense. Practice asking these key questions before giving your answers, the process will feel more natural and you will be light years ahead of the other job candidates you're competing with.
After uncovering what the employer is looking for, describe why the needs of this job bear striking parallels to tasks you've succeeded at before. Be sure to illustrate with specific examples of your responsibilities and especially your achievements, all of which are geared to present yourself as a perfect match for the needs he has just described.

Question 2 What are your greatest strengths?
TRAPS: This question seems like a softball lob, but be prepared. You don't want to come across as egotistical or arrogant. Neither is this a time to be humble.
BEST ANSWER: You know that your key strategy is to first uncover your interviewer's greatest wants and needs before you answer questions. And from Question 1, you know how to do this.
Prior to any interview, you should have a list mentally prepared of your greatest strengths. You should also have, a specific example or two, which illustrates each strength, an example chosen from your most recent and most impressive achievements.
You should, have this list of your greatest strengths and corresponding examples from your achievements so well committed to memory that you can recite them cold after being shaken awake at 2:30AM.
Then, once you uncover your interviewer's greatest wants and needs, you can choose those achievements from your list that best match up.
As a general guideline, the 10 most desirable traits that all employers love to see in their
employees are:
1. A proven track record as an achiever...especially if your achievements match
up with the employer's greatest wants and needs.
2. Intelligence...management "savvy".
3. Honesty...integrity...a decent human being.
4. Good fit with corporate culture...someone to feel comfortable with...a team
player who meshes well with interviewer's team.
5. Likeability...positive attitude...sense of humor.
6. Good communication skills.
7. Dedication...willingness to walk the extra mile to achieve excellence.
8. Definiteness of purpose...clear goals.
9. Enthusiasm...high level of motivation.
10. Confident...healthy...a leader.

Question 3 What are your greatest weaknesses?
TRAPS: Beware - this is an eliminator question, designed to shorten the candidate list.
Any admission of a weakness or fault will earn you an “A” for honesty, but an “F” for the interview.

PASSABLE ANSWER: Disguise a strength as a weakness.
Example: “I sometimes push my people too hard. I like to work with a sense of urgency and everyone is not always on the same wavelength.”
Drawback: This strategy is better than admitting a flaw, but it's so widely used, it is
transparent to any experienced interviewer.
BEST ANSWER: (and another reason it's so important to get a thorough description of your interviewer's needs before you answer questions): Assure the interviewer that you can think of nothing that would stand in the way of your performing in this position with excellence. Then, quickly review you strongest qualifications.

Example: “Nobody's perfect, but based on what you've told me about this position, I believe I' d make an outstanding match. I know that when I hire people, I look for two things most of all. Do they have the qualifications to do the job well, and the motivation to do it well? Everything in my background shows I have both the qualifications and a strong desire to achieve excellence in whatever I take on. So I can say in all honesty that I see nothing that would cause you even a small concern about my ability or my strong
desire to perform this job with excellence.”
Alternate strategy (if you don't yet know enough about the position to talk about such a
perfect fit):
Instead of confessing a weakness, describe what you like most and like least, making sure that what you like most matches up with the most important qualification for success in the position, and what you like least is not essential.
Example: Let's say you're applying for a teaching position. “If given a choice, I like to spend as much time as possible in front of my prospects selling, as opposed to shuffling paperwork back at the office. Of course, I long ago learned the importance of filing paperwork properly, and I do it conscientiously. But what I really love to do is sell (if your interviewer were a sales manager, this should be music to his ears.)

Question 4 Tell me about something you did – or failed to do – that you now feel a little ashamed of.
TRAPS: There are some questions your interviewer has no business asking, and this is one. But while you may feel like answering, “none of your business,” naturally you can’t. Some interviewers ask this question on the chance you admit to something, but if not, at least they’ll see how you think on your feet.
Some unprepared candidates, flustered by this question, unburden themselves of guilt from their personal life or career, perhaps expressing regrets regarding a parent,spouse, child, etc. All such answers can be disastrous.
BEST ANSWER: As with faults and weaknesses, never confess a regret. But don’t seem as if you’re stonewalling either.
Best strategy: Say you harbor no regrets, then add a principle or habit you practice regularly for healthy human relations.
Example: Pause for reflection, as if the question never occurred to you. Then say, “You know, I really can’t think of anything.” (Pause again, then add): “I would add that as a general management principle, I’ve found that the best way to avoid regrets is to avoid causing them in the first place. I practice one habit that helps me a great deal in this regard. At the end of each day, I mentally review the day’s events and conversations to
take a second look at the people and developments I’m involved with and do a doublecheck of what they’re likely to be feeling. Sometimes I’ll see things that do need more follow-up, whether a pat on the back, or maybe a five minute chat in someone’s office to make sure we’re clear on things…whatever.”
“I also like to make each person feel like a member of an elite team, like the Boston Celtics or LA Lakers in their prime. I’ve found that if you let each team member know you expect excellence in their performance…if you work hard to set an example yourself…and if you let people know you appreciate and respect their feelings, you wind up with a highly motivated group, a team that’s having fun at work because they’re striving for excellence rather than brooding over slights or regrets.”

Question 5 Why are you leaving (or did you leave) this position?

TRAPS: Never badmouth your previous industry, company, board, boss, staff,

employees or customers. This rule is inviolable: never be negative. Any mud you hurl

will only soil your suit.

Especially avoid words like “personality clash”, “didn’t get along”, or others which cast a

shadow on your competence, integrity, or temperament.

BEST ANSWER:

(If you have a job presently)

If you’re not yet 100% committed to leaving your present post, don’t be afraid to say so.

Since you have a job, you are in a stronger position than someone who does not. But

don’t be coy either. State honestly what you’d be hoping to find in a new spot. Of

course, as stated often before, you answer will all the stronger if you have already

uncovered what this position is all about and you match your desires to it.

(If you do not presently have a job.)

Never lie about having been fired. It’s unethical – and too easily checked. But do try to

deflect the reason from you personally. If your firing was the result of a takeover,

merger, division wide layoff, etc., so much the better.

But you should also do something totally unnatural that will demonstrate consummate

professionalism. Even if it hurts , describe your own firing – candidly, succinctly and

without a trace of bitterness – from the company’s point-of-view, indicating that you

could understand why it happened and you might have made the same decision

yourself.

Your stature will rise immensely and, most important of all, you will show you are healed

from the wounds inflicted by the firing. You will enhance your image as first-class

management material and stand head and shoulders above the legions of firing victims

who, at the slightest provocation, zip open their shirts to expose their battle scars and decry the unfairness of it all.

For all prior positions:

Make sure you’ve prepared a brief reason for leaving. Best reasons: more money,opportunity, responsibility or growth.

Question 6 The “Silent Treatment”
TRAPS: Beware – if you are unprepared for this question, you will probably not handle
it right and possibly blow the interview. Thank goodness most interviewers don’t employ
it. It’s normally used by those determined to see how you respond under stress. Here’s
how it works:
You answer an interviewer’s question and then, instead of asking another, he just stares
at you in a deafening silence.
You wait, growing a bit uneasy, and there he sits, silent as Mt. Rushmore, as if he
doesn’t believe what you’ve just said, or perhaps making you feel that you’ve unwittingly
violated some cardinal rule of interview etiquette.
When you get this silent treatment after answering a particularly difficult question , such
as “tell me about your weaknesses”, its intimidating effect can be most disquieting, even
to polished job hunters.
Most unprepared candidates rush in to fill the void of silence, viewing prolonged,
uncomfortable silences as an invitation to clear up the previous answer which has
obviously caused some problem. And that’s what they do – ramble on, sputtering more
and more information, sometimes irrelevant and often damaging, because they are
suddenly playing the role of someone who’s goofed and is now trying to recoup. But
since the candidate doesn’t know where or how he goofed, he just keeps talking,
showing how flustered and confused he is by the interviewer’s unmovable silence.
BEST ANSWER: Like a primitive tribal mask, the Silent Treatment loses all it power to
frighten you once you refuse to be intimidated. If your interviewer pulls it, keep quiet
yourself for a while and then ask, with sincere politeness and not a trace of sarcasm, “Is
there anything else I can fill in on that point?” That’s all there is to it.
Whatever you do, don’t let the Silent Treatment intimidate you into talking a blue streak,
because you could easily talk yourself out of the position.
Question 7 Why should I hire you?

TRAPS: Believe it or not, this is a killer question because so many candidates are
unprepared for it. If you stammer or adlib you’ve blown it.

BEST ANSWER: By now you can see how critical it is to apply the overall strategy of
uncovering the employer’s needs before you answer questions. If you know the
employer’s greatest needs and desires, this question will give you a big leg up over other
candidates because you will give him better reasons for hiring you than anyone else is
likely to…reasons tied directly to his needs.
Whether your interviewer asks you this question explicitly or not, this is the most
important question of your interview because he must answer this question favorably in
is own mind before you will be hired. So help him out! Walk through each of the position’s requirements as you understand them, and follow each with a reason why you
meet that requirement so well.
Example: “As I understand your needs, you are first and foremost looking for someone
who can manage the sales and marketing of your book publishing division. As you’ve
said you need someone with a strong background in trade book sales. This is where
I’ve spent almost all of my career, so I’ve chalked up 18 years of experience exactly in
this area. I believe that I know the right contacts, methods, principles, and successful
management techniques as well as any person can in our industry.”
“You also need someone who can expand your book distribution channels. In my prior
post, my innovative promotional ideas doubled, then tripled, the number of outlets selling
our books. I’m confident I can do the same for you.”
“You need someone to give a new shot in the arm to your mail order sales, someone
who knows how to sell in space and direct mail media. Here, too, I believe I have
exactly the experience you need. In the last five years, I’ve increased our mail order
book sales from $600,000 to $2,800,000, and now we’re the country’s second leading
marketer of scientific and medical books by mail.” Etc., etc., etc.,
Every one of these selling “couplets” (his need matched by your qualifications) is a
touchdown that runs up your score. IT is your best opportunity to outsell your
competition.

Question 8 Aren’t you overqualified for this position?

TRAPS: The employer may be concerned that you’ll grow dissatisfied and leave.
BEST ANSWER: As with any objection, don’t view this as a sign of imminent defeat.
It’s an invitation to teach the interviewer a new way to think about this situation, seeing
advantages instead of drawbacks.
Example: “I recognize the job market for what it is – a marketplace. Like any
marketplace, it’s subject to the laws of supply and demand. So ‘overqualified’ can be a
relative term, depending on how tight the job market is. And right now, it’s very tight. I
understand and accept that.”
“I also believe that there could be very positive benefits for both of us in this match.”
“Because of my unusually strong experience in ________________ , I could start to
contribute right away, perhaps much faster than someone who’d have to be brought
along more slowly.”
“There’s also the value of all the training and years of experience that other companies
have invested tens of thousands of dollars to give me. You’d be getting all the value of
that without having to pay an extra dime for it. With someone who has yet to acquire
that experience, he’d have to gain it on your nickel.”

“I could also help you in many things they don’t teach at the Harvard Business School.
For example…(how to hire, train, motivate, etc.) When it comes to knowing how to work
well with people and getting the most out of them, there’s just no substitute for what you
learn over many years of front-line experience. You company would gain all this, too.”
“From my side, there are strong benefits, as well. Right now, I am unemployed. I want
to work, very much, and the position you have here is exactly what I love to do and am
best at. I’ll be happy doing this work and that’s what matters most to me, a lot more that
money or title.”
“Most important, I’m looking to make a long term commitment in my career now. I’ve had
enough of job-hunting and want a permanent spot at this point in my career. I also know
that if I perform this job with excellence, other opportunities cannot help but open up for
me right here. In time, I’ll find many other ways to help this company and in so doing,
help myself. I really am looking to make a long-term commitment.”
NOTE: The main concern behind the “overqualified” question is that you will leave your
new employer as soon as something better comes your way. Anything you can say to
demonstrate the sincerity of your commitment to the employer and reassure him that
you’re looking to stay for the long-term will help you overcome this objection.

Question 9 Where do you see yourself five years from now?

TRAPS: One reason interviewers ask this question is to see if you’re settling for this
position, using it merely as a stopover until something better comes along. Or they
could be trying to gauge your level of ambition.
If you’re too specific, i.e., naming the promotions you someday hope to win, you’ll sound
presumptuous. If you’re too vague, you’ll seem rudderless.
BEST ANSWER: Reassure your interviewer that you’re looking to make a long-term
commitment…that this position entails exactly what you’re looking to do and what you do
extremely well. As for your future, you believe that if you perform each job at hand with
excellence, future opportunities will take care of themselves.
Example: “I am definitely interested in making a long-term commitment to my next
position. Judging by what you’ve told me about this position, it’s exactly what I’m looking
for and what I am very well qualified to do. In terms of my future career path, I’m
confident that if I do my work with excellence, opportunities will inevitable open up for
me. It’s always been that way in my career, and I’m confident I’ll have similar
opportunities here.”

Question 10 Describe your ideal company, location and job.

TRAPS: This is often asked by an experienced interviewer who thinks you may be
overqualified, but knows better than to show his hand by posing his objection directly.
So he’ll use this question instead, which often gets a candidate to reveal that, indeed, he
or she is looking for something other than the position at hand.
BEST ANSWER: The only right answer is to describe what this company is offering,
being sure to make your answer believable with specific reasons, stated with sincerity,
why each quality represented by this opportunity is attractive to you.
Remember that if you’re coming from a company that’s the leader in its field or from a
glamorous or much admired company, industry, city or position, your interviewer and his
company may well have an “Avis” complex. That is, they may feel a bit defensive about
being “second best” to the place you’re coming from, worried that you may consider
them bush league.
This anxiety could well be there even though you’ve done nothing to inspire it. You must
go out of your way to assuage such anxiety, even if it’s not expressed, by putting their
virtues high on the list of exactly what you’re looking for, providing credible reason for
wanting these qualities.
If you do not express genuine enthusiasm for the firm, its culture, location, industry, etc.,
you may fail to answer this “Avis” complex objection and, as a result, leave the
interviewer suspecting that a hot shot like you, coming from a Fortune 500 company in
New York, just wouldn’t be happy at an unknown manufacturer based in Topeka,
Kansas.

Question 11 Why do you want to work at our company?

TRAPS: This question tests whether you’ve done any homework about the firm. If you
haven’t, you lose. If you have, you win big.
BEST ANSWER: This question is your opportunity to hit the ball out of the park, thanks
to the in-depth research you should do before any interview.
Best sources for researching your target company: annual reports, the corporate
newsletter, contacts you know at the company or its suppliers, advertisements, articles
about the company in the trade press.

Question 12 What are your career options right now?

TRAPS: The interviewer is trying to find out, “How desperate are you?”
BEST ANSWER: Prepare for this question by thinking of how you can position yourself
as a desired commodity. If you are still working, describe the possibilities at your
present firm and why, though you’re greatly appreciated there, you’re looking for
something more (challenge, money, responsibility, etc.). Also mention that you’re
seriously exploring opportunities with one or two other firms.
If you’re not working, you can talk about other employment possibilities you’re actually
exploring. But do this with a light touch, speaking only in general terms. You don’t want
to seem manipulative or coy.

Question 13 Why have you been out of work so long?

TRAPS: A tough question if you’ve been on the beach a long time. You don’t want to
seem like damaged goods.
BEST ANSWER: You want to emphasize factors which have prolonged your job search
by your own choice.
Example: “After my job was terminated, I made a conscious decision not to jump on the
first opportunities to come along. In my life, I’ve found out that you can always turn a
negative into a positive IF you try hard enough. This is what I determined to do. I
decided to take whatever time I needed to think through what I do best, what I most want
to do, where I’d like to do it…and then identify those companies that could offer such an
opportunity.”
“Also, in all honesty, you have to factor in the recession (consolidation, stabilization, etc.)
in the (banking, financial services, manufacturing, advertising, etc.) industry.”
“So between my being selective and the companies in our industry downsizing, the
process has taken time. But in the end, I’m convinced that when I do find the right
match, all that careful evaluation from both sides of the desk will have been well
worthwhile for both the company that hires me and myself.

Question 14 Tell me honestly about the strong points and weak points of your boss (company, management team,
etc.)…

TRAPS: Skillfull interviewers sometimes make it almost irresistible to open up and air a
little dirty laundry from your previous position. DON’T
BEST ANSWER: Remember the rule: Never be negative. Stress only the good points,
no matter how charmingly you’re invited to be critical.
Your interviewer doesn’t care a whit about your previous boss. He wants to find out how
loyal and positive you are, and whether you’ll criticize him behind his back if pressed to
do so by someone in this own company. This question is your opportunity to
demonstrate your loyalty to those you work with.

Question 15 What good books have you read lately?

TRAPS: As in all matters of your interview, never fake familiarity you don’t have. Yet
you don’t want to seem like a dullard who hasn’t read a book since Tom Sawyer.
BEST ANSWER: Unless you’re up for a position in academia or as book critic for The
New York Times, you’re not expected to be a literary lion. But it wouldn’t hurt to have
read a handful of the most recent and influential books in your profession and on
management.
Consider it part of the work of your job search to read up on a few of these leading
books. But make sure they are quality books that reflect favorably upon you, nothing
that could even remotely be considered superficial. Finally, add a recently published
bestselling work of fiction by a world-class author and you’ll pass this question with flying
colors.

Question 16 Tell me about a situation when your work was
criticized.

TRAPS: This is a tough question because it’s a more clever and subtle way to get you
to admit to a weakness. You can’t dodge it by pretending you’ve never been criticized.
Everybody has been. Yet it can be quite damaging to start admitting potential faults and
failures that you’d just as soon leave buried.
This question is also intended to probe how well you accept criticism and direction.
BEST ANSWERS: Begin by emphasizing the extremely positive feedback you’ve gotten
throughout your career and (if it’s true) that your performance reviews have been
uniformly excellent.
Of course, no one is perfect and you always welcome suggestions on how to improve
your performance. Then, give an example of a not-too-damaging learning experience
from early in your career and relate the ways this lesson has since helped you. This
demonstrates that you learned from the experience and the lesson is now one of the
strongest breastplates in your suit of armor.
If you are pressed for a criticism from a recent position, choose something fairly trivial
that in no way is essential to your successful performance. Add that you’ve learned from
this, too, and over the past several years/months, it’s no longer an area of concern
because you now make it a regular practice to…etc.
Another way to answer this question would be to describe your intention to broaden your
master of an area of growing importance in your field. For example, this might be a
computer program you’ve been meaning to sit down and learn… a new management
technique you’ve read about…or perhaps attending a seminar on some cutting-edge
branch of your profession.
Again, the key is to focus on something not essential to your brilliant performance but
which adds yet another dimension to your already impressive knowledge base.

Question 17 What are your outside interests?
TRAPS: You want to be a well-rounded, not a drone. But your potential employer
would be even more turned off if he suspects that your heavy extracurricular load will
interfere with your commitment to your work duties.
BEST ANSWERS: Try to gauge how this company’s culture would look upon your
favorite outside activities and be guided accordingly.
You can also use this question to shatter any stereotypes that could limit your chances.
If you’re over 50, for example, describe your activities that demonstrate physical
stamina. If you’re young, mention an activity that connotes wisdom and institutional
trust, such as serving on the board of a popular charity.
But above all, remember that your employer is hiring your for what you can do for him,
not your family, yourself or outside organizations, no matter how admirable those
activities may be.

Question 18 The “Fatal Flaw” question

TRAPS: If an interviewer has read your resume carefully, he may try to zero in on a
“fatal flaw” of your candidacy, perhaps that you don’t have a college degree…you’ve
been out of the job market for some time…you never earned your CPA, etc.
A fatal flaw question can be deadly, but usually only if you respond by being overly
defensive.
BEST ANSWERS: As every master salesperson knows, you will encounter objections
(whether stated or merely thought) in every sale. They’re part and parcel of the buyer’s
anxiety. The key is not to exacerbate the buyer’s anxiety but diminish it. Here’s how…
Whenever you come up against a fatal flaw question:
1. Be completely honest, open and straightforward about admitting the
shortcoming. (Showing you have nothing to hide diminishes the buyer’s
anxiety.)
2. Do not apologize or try to explain it away. You know that this supposed flaw
is nothing to be concerned about, and this is the attitude you want your
interviewer to adopt as well.
3. Add that as desirable as such a qualification might be, its lack has made you
work all the harder throughout your career and has not prevented you from
compiling an outstanding tack record of achievements. You might even give
examples of how, through a relentless commitment to excellence, you have
consistently outperformed those who do have this qualification.
Of course, the ultimate way to handle “fatal flaw” questions is to prevent them from
arising in the first place. You will do that by following the master strategy described in
Question 1, i.e., uncovering the employers needs and them matching your qualifications
to those needs.
Once you’ve gotten the employer to start talking about his most urgently-felt wants and
goals for the position, and then help him see in step-by-step fashion how perfectly your
background and achievements match up with those needs, you’re going to have one
very enthusiastic interviewer on your hands, one who is no longer looking for “fatal
flaws”.'

Question 19 How do you feel about reporting to a younger person (minority, woman, etc)?
TRAPS: It’s a shame that some interviewers feel the need to ask this question, but
many understand the reality that prejudices still exist among some job candidates, and
it’s better to try to flush them out beforehand.
The trap here is that in today’s politically sensitized environment, even a well-intentioned
answer can result in planting your foot neatly in your mouth. Avoid anything which
smacks of a patronizing or an insensitive attitude, such as “I think they make terrific
bosses” or “Hey, some of my best friends are…”
Of course, since almost anyone with an IQ above room temperature will at least try to
steadfastly affirm the right answer here, your interviewer will be judging your sincerity
most of all. “Do you really feel that way?” is what he or she will be wondering.
So you must make your answer believable and not just automatic. If the firm is wise
enough to have promoted peopled on the basis of ability alone, they’re likely quite proud
of it, and prefer to hire others who will wholeheartedly share their strong sense of fair
play.
BEST ANSWER: You greatly admire a company that hires and promotes on merit alone
and you couldn’t agree more with that philosophy. The age (gender, race, etc.) of the
person you report to would certainly make no difference to you.
Whoever has that position has obviously earned it and knows their job well. Both the
person and the position are fully deserving of respect. You believe that all people in a
company, from the receptionist to the Chairman, work best when their abilities, efforts
and feelings are respected and rewarded fairly, and that includes you. That’s the best
type of work environment you can hope to find.

CCNA Router Commands

2010-05-15T04:32:00.000-07:00

CCNA Router Commands for the 640−607 exam (version 1.0)

BasicsEnter Privileged Exec Mode enable

Leave Privileged Exec Mode and go back to User Mode disable

Log out of the router, end the console session,same as exit command exit

Log out of the router, end the console session, same as logout command logout

Setup a basic configuration by answering questions setup

Show the current configuration stored in RAM show running−config

Show the startup configuration stored in NVRAM show startup−config

Display IOS version (configuration register value is also displayed) show version

Show IOS files stored in flash and available free space show flash

Save the current configuration into NVRAM copy running−config startup−config

Use the startup configuration stored in NVRAM                                copy startup−config running−config
Load a saved configuration from a TFTP server into NVRAM              copy tftp running−config
Upgrade the IOS stored in flash from an image stored on a TFTP server copy tftp flash
Create a backup of router IOS and store it in a file on a TFTP server      copy flash tftp
Instruct the router to boot from a specific IOS image stored in flash       boot system flash [filename]
Instruct the router to boot from a specific IOS image stored on a TFTP server boot system tftp [filename]
Enter Global Configuration Mode                                                      config terminal
Set a Message−of−the−day banner to be displayed before the user logs in to the router
banner motd # message #
Set a login message to be displayed before the user logs in to the router    banner login # message #
Set a banner to be displayed after the user logs in to the router                 banner exec # message #
(incoming is displayed with a reverse telnet connection, exec with all others) banner incoming # message #
Give the router a hostname (default is router)                                      hostname [name]
Disable DNS lookups (enabled by default)                                        no ip domain−lookup
Change the size of the history buffer (default is 10 commands)           terminal history size 20

PASSWORDS :-

Set a password for Privileged Exec Mode                     enable password [password]
Set an encrypted password for Privileged Exec Mode    enable secret [password]
Set password TELNET access                                       line vty 0 4
login                                                                               password [passwords]
Set a password for Console Port access                       line console 0 login password [passwords]

INTERFACE CONFIGURATION:-

Configure the interface Ethernet 0                              interface e 0
Configure the first Serial interface                               interface s 0
Configure the second Token Ring interface                 interface t 1
Enable an interface                                                     no shutdown
Disable an interface                                                    shutdown
Set the clock rate on a DCE (make a router a DCE)  clock rate 64000
Set the bandwidth                                                      bandwidth 64
Display the status of an interface                                 show interface serial 1
Display DTE/DCE state                                             show controller serial 1
Set keepalive period                                                  keepalive 10

IP CONFIGURATION:-
Disable IP routing (IP routing is enabled by default)                no ip routing
Display IP routing table                                                          show ip route
Configure an interface with an IP address                              ip address 192.168.1.12 255.255.255.0
Enable RIP                                                                           router rip
                                                                                            network [network−address1]
                                                                                           network [network−address2…]
Enable RIP Triggered updates (only send updates when routing table has changed instead of every 30 seconds)                                                                             ip rip triggered
Disable automatic route summarization                               no auto−summary
Enable IGRP                                                                     router igrp [as−number]
                                                                                         network [network−address1]
                                                                                          network [network−address2…]

DHCP Instalaltion

2010-02-05T01:30:00.000-08:00

Installing DHCP in Windows Server 2003:-
In my last artical I have discuss about the Basic of DHCP server , IP assignment process, DORA etc. Click here to know about the basic of DHCP and DORA process.
After completing this topic, you should be able to follow the steps to install the DHCP service. 1. DHCP installation:-
Before you install DHCP you need to ensure that there is a static IP address on the server and that you know the range of IP addresses that you will manually configure to be used in the IP address pool.
Note
To install DHCP, you need to have administrative rights on the server.
Installing DCHP involves
· accessing the Add/Remove Windows Components feature
· selecting DHCP from Networking Services
· running the DHCP wizard
To access the Add/Remove Windows Components feature, you select Start - Control Panel.
In the Control Panel window, you can access a range of configuration options. In this case, you double-click the Add/Remove Programs icon.
In the Add or Remove Programs window, you can add, change or remove programs and Windows components. You want to add the Windows DHCP option.
You click Add/Remove Windows Components or you press Alt+W.
The Windows Components Wizard allows you to add or remove Windows components.
In the Components list box you scroll to Networking Services to access the DHCP option for installation.
You select Networking Services and click the Details button or press Alt+D.
The Networking Services dialog box lists protocols that are subcomponents of Windows networking services.
In the Networking Services dialog box, you select Dynamic Host Configuration Protocol (DHCP) and then you click OK to confirm your choice
The Networking Services checkbox is selected and you could choose to add or remove other Windows components at this point.
In this case, you don't want to configure additional components and so you click Next to begin the installation.
The wizard automatically installs the DHCP components.
Once the installation is complete, the Finish page appears, and you click Finish to complete the installation.
You return to the Add or Remove Programs window and can now configure and authorize the DHCP server.
2. Authorizing DHCP
Historically, many network problems were caused by incorrectly configured DHCP servers being set up on the network. These rogue DHCP servers are active DHCP servers with incorrect IP address pools that can seriously disrupt network functioning.To prevent this, Windows Server 2003 requires you to authorize a DHCP server in Active Directory before it can become active on a network. Each time a DHCP service starts up, it checks in Active Directory to verify that it is authorized to do so.
Suppose that you have recently installed DHCP, and you now want to place the server online on the network. To do this you need to open the DHCP console, and authorize the DHCP server.
To open the DHCP console, you select Start - Administrative Tools - DHCP.
Because you have not yet configured the server, the DHCP console lists only the server and no other information is available.
To authorize the DHCP server, you select Authorize from the Action menu or you press Alt+A+Z.
In the console navigation pane, a green up-pointing arrow on the server icon indicates that the server is now authorized as a DHCP server.
When you select the DHCP node in the Navigation pane, the details pane shows the status of the server as running.
3. The DHCP console
Once the DHCP server software is installed, you can manage the DHCP service from the DHCP console.You can create, modify, and manage various DHCP scopes and TCP/IP configuration options. Once you created a scope on a newly installed DHCP server, you can access configuration options from the console.
The DHCP console lists servers in the navigation pane, so you can manage multiple DHCP servers from the console.It also lists a Server Options subfolder, in which you can create, list, and manage configuration options specific to each DHCP server.
Once you have created a scope, the DHCP console allows you configure and modify this range of DHCP options:
· Address Pool
· Address leases
· Reservations
· Scope Options
Address Pool
The Address Pool subfolder stores each address pool configured for a scope, including the exclusions defined when creating a scope.Description of Address Pool details pane - Description follows: The pane contains three columns – Start IP address, End IP address, and Description. .
Address leases :-
The Address Leases subfolder lists all address leases that the DHCP server issues. It provides the client IP address, the client name, the lease expiration date, the lease type, and the unique ID.Reservations
The Reservations subfolder lists IP addresses that you have reserved for specific DHCP clients. For example, you can specify particular IP addresses to DNS servers on the network.
Scope Options :-
The Scope Options folder lists any scope options that you have configured. These can include the default gateway for the scope or WINS servers for the scope. Scope options override server options and can be overridden by both Reservations and user class options.
Summary:-
Prerequisites for installing DHCP are a static IP address on the server and the range of IP addresses that should be used in the IP address pool.To prevent rogue DHCP servers, Windows Server 2003 requires you to authorize a DHCP server before it can become active on a network.You can manage the DHCP service from the DHCP console. The console lists all DHCP servers on the network, server options, and scopes.

DHCP Basics

2010-02-04T23:17:00.000-08:00

Introducing Dynamic Host Configuration Protocol (DHCP)

1. DHCP benefits

Without correct and consistent configuration, TCP/IP hosts are unable to communicate successfully.
Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically assigns TCP/IP configuration to client computers on a network. DHCP ensures that each host has a subnet mask, a default gateway, and a unique IP address.
All configuration parameters that DHCP assigns are set on a central DHCP server.
A central DHCP server on a network controls whether the addresses it provides to clients are permanent or leased for a specific period of time.
When a DHCP server allocates leased addresses, clients revalidate their addresses and renew their leases by regularly checking with the DHCP server.
DHCP performs address allocation, leasing, and lease renewal transparently, thereby reducing the need for administrative input in TCP/IP address assignment.
Using DHCP on a network provides a number of significant benefits, including
• lower administrative overhead
• fewer address conflicts
• standards-based multi-platform support
lower administrative overhead
DHCP reduces administrative overhead by automatically assigning IP addresses to clients. It also provides a centralized base for managing and deploying IP address and configuration information.
Deployment is simplified by the inclusion of TCP/IP configuration information – default gateway, DNS suffix, and WINS server information – with each IP address assigned to a client. DHCP servers can register their clients' IP addresses and Fully Qualified Domain Names (FQDNs) with DNS servers on the network.
Fewer address conflicts
DHCP reduces the possibility of address conflicts by automatically assigning IP addresses to TCP/IP clients and monitoring the addresses it assigns. In this way, each assigned address is unique to the network.
Standards-based multi-platform support
DHCP is standards-based and is therefore supported by a range of operating systems and applications. Operation systems that support DHCP include Apple Mac, Linux, Windows, and UNIX.

2. The DORA process
DHCP clients and servers follow a formal request process by which clients obtain an IP address and other configuration information from the DHCP server.
The IP addresses that the DHCP server assigns are taken from a range of IP addresses known as an address pool or a scope.
DHCP also supports scope options, which provide particular addresses to specific systems – for example, a default gateway.
The request process between a DHCP client and server follows four formal steps – Discover, Offer, Request, Acknowledgement (DORA) – that are based on four message types exchanged between the two systems.
• DHCP Discover
• DHCP Offer
• DHCP Request
• DHCP Ack

DHCP Discover:-
When a client joins a network, it broadcasts a DHCP Discover message that contains the client's identity and a request for an IP address. The DHCP Discover message also requests IP configuration information, such as the address of the default gateway, the subnet mask, the domain name, and any static routes. This request is often termed an IP lease request.
All DHCP servers on the network segment receive and respond to a DHCP Discover message. If a single DHCP server is required to service more than one network segment, you need to configure the segment's routers to forward DHCP messages so that they can reach the shared DHCP server on a linked network.
If the routers cannot be configured to forward DHCP messages, then a DHCP relay agent may be configured on the subnet. The relay agent will pick up the Discover messages and forward them directly to the DHCP server.

DHCP Offer:-
Any DHCP server that has spare IP addresses and receives an IP lease request – in the form of a DHCP Discover message – responds by sending a DHCP Offer message to the client.
The DHCP server checks whether an IP address from its pool is in use on the network. If the address is unassigned, it then reserves the IP address until the client has accepted or rejected the offer.
Before sending a DHCP Offer, the DHCP server checks its scope details to see if a reservation exists for the client. If a reservation exists and the clients MAC address matches it, then the DHCP server offers the IP address corresponding to the reservation.
Clients may receive several offers from different DHCP servers but normally accept the first offer that they receive.

DHCP Request:-
Once a client has received and accepted a DHCP Offer message, it sends a DHCP Request message, asking to be assigned the IP address that the server offered. When the DHCP server receives the DHCP Request that accepts the IP address, the server marks the address as leased.
If a DHCP server receives a DHCP Request message stating that the client has accepted another server's offer or if the server does not receive a response within the allocated time, it returns the address to the address pool.

DHCP Ack:-
When a selected DHCP server receives an acceptance DHCP Request message and marks an address as leased, it generates a DHCP Ack message.
The DHCP Ack message confirms the client's address and includes additional configuration information for the client.
The client then checks this information and if it is valid, the client configures itself with the IP address and configuration information and can now communicate on the network.

The DORA process between client and server must move through each of the four steps:-

The client configures itself to use the IP address once it receives the DHCP Ack message. In the DHCP Request message the client accepts or rejects an IP address offer and the server receives the request for an IP address in the DHCP Discover message. The server sends an IP address to the client using the DHCP Offer message.
The DHCP Ack message contains confirmation of the IP address lease and further configuration information. If the client accepts this information as valid, it forms a binding relationship with the server and starts using its IP address lease.
The DHCP Discover message is a broadcast request by the client for an IP address lease.
The DHCP Offer message is sent by the server and contains an available IP address, which is offered to the client.
The DHCP Request message is sent by a client in response to a DHCP server's offer of an IP address. The client can respond by requesting or rejecting the IP address and lease offered by the server.

3. Lease renewal and reservations
A DHCP lease is a configurable time-span during which a client has permission to use a particular IP address. The default lease duration in Windows Server 2003 is eight days.
However, clients monitor when their lease is due to expire. When a lease is halfway through, a client sends a renewal request to the DHCP server.

If the renewal is approved, the client receives a DHCP Ack with a new expiry date. If the request is denied, the client attempts another lease renewal when the lease is 87.5 percent complete.
If a client's second renewal request fails, then the client will continue to use its current IP configuration until the lease expires.
When the lease expires, the client starts the DORA cycle from the beginning.
When a DHCP client with an active IP address lease is moved to a new or different subnet, it is unable to communicate on that subnet.
To ensure that a client reconfigures its lease settings, you need to manually release and renew the lease.
To manually release and renew the lease you type ipconfig /release followed by ipconfig /renew at the command prompt.
Relay agents are typically routers configured to forward Bootstrap Protocol (BOOTP) and DHCP requests to a DHCP server on a separate subnet.
The relay agents are configured with the DHCP server's address and forward DHCP packets

Summary:-
Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically assigns TCP/IP configuration to client computers on a network. The DHCP client and server applications are responsible for address allocation, leasing, and lease renewal. Benefits of DHCP include lower administrative overhead, fewer address conflicts, and standards-based multi-platform support.
DHCP clients and servers follow a formal request process by which clients obtain an IP address and other configuration information through the server. This process involves DHCP Discover, Offer, Request, and Ack messages and is known as DORA.
A DHCP lease is a configurable time-span during which a client has permission to use a particular IP address. When a DHCP client with an active IP address lease is moved to a new or different subnet, it is necessary to manually release and renew its lease. Additionally, relay agents can allow a single DHCP server to service clients across where the routers cannot forward DHCP messages.

Router IOS Recovery using TFTP server

2010-01-19T00:48:00.000-08:00

Router IOS Recovery using TFTP server:-
This will help you to install the router IOS to a Cisco 2500/2600/2800/3800 series routers. First make sure, you have installed and configured any TFTP (Trivial File Transfer Protocol) server in the computer where you will attach your router for recovery. To download TFTP Server software ,Click Here. After downloading and installing the TFTP server, connect your router with this pc using one Console cable and one LAN cable.LAN cable can be attached on any Ethernet port of the router. Now start the HYPERTERMINAL utility and bootup your router.
If you are trying to boot up your router without an IOS, the nonworking router will boot up in ROMMON mode and the router first prompt will look like this:

rommon>

Now type the following information, for example router ip address, mask and default gateway then tftp server address.

rommon 3 > IP_ADDRESS=10.1.1.2 (router ip address)
rommon 4 > IP_SUBNET_MASK=255.0.0.0 (default subnet mask)
rommon 5 > DEFAULT_GATEWAY=10.1.1.1 (gateway address)
rommon 6 > TFTP_SERVER=10.1.1.1 (tftp server address)
rommon 7 > TFTP_FILE=12.0(4)t (IOS file name)

Make sure that IP Address of your PC to which you have connected the router and you install the tftp server should be of same series. To get the detail knowledge of IP Addressing (Click here)

Now again run the tftpdnld command to start recovery process immediately.

rommon 8 > tftpdnld
IP_ADDRESS: 10.1.1.2
IP_SUBNET_MASK: 255.0.0.0
DEFAULT_GATEWAY: 10.1.1.2
TFTP_SERVER: 10.1.1.1
TFTP_FILE: 12.0(4)t
Invoke this command for disaster recovery only.
WARNING: all existing data in all partitions on flash will be lost!
Do you wish to continue? y/n: [n]: Yes
Receiving 12.0(4)t from 10.1.1.1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
File reception completed.
Copying file 12.0(4)t to flash.
Erasing flash at 0x60100000
Now run the reset command to restore router as factory default settings.
rommon 16 > reset
Now after some time, your router will boot up with factory default settings.

To tidy that up here is the full list of commands to issue at the ROMMON command line to copy a IOS from a TFTP server

copying the IOS using TFTP (only works on some routers with a more modem Boot Flash)

IP_ADDRESS=IP address of the Ethernet port

IP_SUBNET_MASK=subnet mask of the Ethernet port

DEFAULT_GATEWAY=The IP address of your Local Computer or TFTP Server

TFTP_SERVER=the IP of the TFTP server (your local computer)

TFTP_FILE=the file name of the IOS file.

tftpdnld

Just make sure you have the TFTP server running on a pc and the required IOS ready to go.

Network Cables

2009-12-07T01:25:00.000-08:00

The two most common unshielded twisted-pair (UTP) network standards are the10 Mhz 10BASE-T Ethernet and the 100Mhz 100BASE-TX Fast Ethernet. The 100BASE-TX standard is quickly becoming the predominant LAN standard. If you are starting from scratch, to build a small home or office network, this is clearly the standard you should choose. This article will show you how to make cables which will work with both standards.

ABOUT LAN :- A LAN can be as simple as two computers, each having a network interface card (NIC) or network adapter and running network software, connected together with a crossover cable.
The next step up would be a network consisting of three or more computers and a hub. Each of the computers is plugged into the hub with a straight-thru cable (the crossover function is performed by the hub).

About cables and connector :- CAT 5 cable has four twisted pairs of wire for a total of eight individually insulated wires. Each pair is color coded with one wire having a solid color (blue, orange, green, or brown) twisted around a second wire with a white background and a stripe of the same color. The solid colors may have a white stripe in some cables. Cable colors are commonly described using the background color followed by the color of the stripe; e.g., white-orange is a cable with a white background and an orange stripe.
The straight through and cross-over patch cables discussed in this article are terminated with CAT 5 RJ-45 modular plugs. RJ-45 plugs are similar to those you'll see on the end of your telephone cable except they have eight versus four or six contacts on the end of the plug and they are about twice as big. Make sure they are rated for CAT 5 wiring. (RJ means "Registered Jack"). Also, there are RJ-45 plugs designed for both solid core wire and stranded wire. Others are designed specifically for one kind of wire or the other. Be sure you buy plugs appropriate for the wire you are going to use. I use plugs designed to accommodate both kinds of wire.

Modular Plug Crimp Tool. You will need a modular crimp tool. This one is very similar to the one I have been using for many years for all kinds of telephone cable work and it works just fine for Ethernet cables. You don't need a lot of bells and whistles, just a tool which will securely crimp RJ-45 connectors. Even though the crimper has cutters which can be used to cut the cable and individual wires, and possibly stripping the outer jacket, I find that the following tools are better for stripping and cutting the cable.
COLOR-CODE STANDARDS :-Let's start with simple pin-out diagrams of the two types of UTP Ethernet cables and watch how committees can make a can of worms out of them. Here are the diagrams:
Note that the TX (transmitter) pins are connected to corresponding RX (receiver) pins, plus to plus and minus to minus. And that you must use a crossover cable to connect units with identical interfaces. If you use a straight-through cable, one of the two units must, in effect, perform the cross-over function.
Note that pins 4, 5, 7, and 8 and the blue and brown pairs are not used in either standard. Quite contrary to what you may read elsewhere, these pins and wires are not used or required to implement 100BASE-TX duplexing--they are just plain wasted.
Now, all you need to remember, to properly configure the cables, are the diagrams for the two cable ends and the following rules:

A straight-thru cable has identical ends
A crossover cable has different ends.
LET'S MAKE SOME CABLES:-
1. Pull the cable off the reel to the desired length and cut.
2. Spread and arrange the pairs roughly in the order of the desired cable end.
3. Untwist the pairs and arrange the wires in the order of the desired cable end. Flatten the end between your thumb and forefinger. Trim the ends of the wires so they are even with one another. It is very important that the unstripped (untwisted) end be slightly less than 1/2" long. If it is longer than 1/2" it will be out-of-spec and susceptible to crosstalk. If it less than slightly less than 1/2" it will not be properly clinched when RJ-45 plug is crimped on.. Flatten again. There should be little or no space between the wires.
Hold the wire near the RJ-45 plug with the clip down and firmly push it into the left side of the front of the crimper (it will only go in one way). Hold the wire in place squeeze the crimper handles quite firmly. This is what will happen:
(Crimp it once.) The crimper pushes two plungers down on the RJ-45 plug. One forces what amounts to a cleverly designed plastic plug/wedge onto the cable jacket and very firmly clinches it. The other seats the "pins," each with two teeth at its end, through the insulation and into the conductors of their respective wires.
Test the crimp...
If done properly an average person will not be able to pull the plug off the cable with his or her bare hands. And that quite simply, besides lower cost, is the primary advantage of twisted-pair cables over the older thinwire, coaxial cables. In fact, I would say the RJ-45 and ease of its installation is the main reason coaxial cable is no longer widely used for small Ethernets. But, don't pull that hard on the plug. It could stretch the cable and change its characteristics. Look at the side of the plug and see if it looks like the diagram and give it a fairly firm tug to make sure it is crimped well.

Networking Standards

2009-12-03T02:37:00.000-08:00

NETWORKING STANDARDS

10Base2 :-
10-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10Base2, which is part of the IEEE 802.3 specification, has a distance limit of 606.8 feet (185 meters) per segment.

10Base5 :-

10-Mbps baseband Ethernet specification using standard (thick) 50-ohm baseband coaxial cable. 10Base5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 1640 feet (500 meters) per segment.

10BaseF:-

10-Mbps baseband Ethernet specification that refers to the 10BaseFB, 10BaseFL, and 10BaseFP standards for Ethernet over fiber-optic cabling.

10BaseT :-

10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Categories 3, 4, or 5): one pair for transmitting data and the other for receiving data. 10BaseT, which is part of the IEEE 802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment.

100BaseT:-

100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BaseT technology on which it is based, 100BaseT sends link pulses over the network segment when no traffic is present. However, these link pulses contain more information than those used in 10BaseT. Based on the IEEE 802.3 standard.

100BaseTX:-

100-Mbps baseband Fast Ethernet specification using two pairs of either UTP or STP wiring. The first pair of wires receives data; the second transmits data. To guarantee the proper signal timing, a 100BaseTX segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard.

100BaseFX:-
A 100-Mbps baseband Fast Ethernet specification using two strands of multimode fiber-optic cable per link. To guarantee proper signal timing, a 100BaseFX link cannot exceed 1312 feet (400 meters) in length. Based on the IEEE 802.3 standard.

Computer Hardware assembly

2009-12-02T23:34:00.000-08:00

Assembling Your Own PC

Assembling your own PC is not hard. I just want to clear that up from the start for example, install memory in systems. Installing memory is an exercise roughly comparable in difficulty to cleaning the lint out of a dryer and putting the filter back in the right way.
Modern computer systems are designed to be easy to fit together, and they are. The majority of components are keyed so they will only fit a certain way, for one thing, and everything is standardized. This is not to say that it is foolproof, but perhaps fool resistant would be true.
This guide aims to be a simple guide to building your own home computer from easily available components available from local, or online retailers. Now, let's get started and show just how easy building your own PC really can be.
Where to begin, and ESD worries :-
If you are a beginner at computers, begin at your local small computer store. For the purposes of buying parts you are much better off dealing with a small store than a large chain or electronic warehouse, provided you get a good feeling about the place when you walk in of course.
Small stores are used to dealing with computers in terms of individual components, so they are better equipped to help you out. Tell them you are planning to build your own PC. They will be able to make sure that the parts you get are compatible, at least. You will have an idea of what you want the computer to do once it's built, so go with that. Once you have all the parts on the list, it's time to start building your computer.
Now, if it seems we've already skipped too many steps for you, I suggest you have a peek at the PCstats ShoppingList - this is a list of gear the staff here draw up each month for a few different price ranges. The ShoppingList consists of computer components we'd actually buy ourselves, and of course you're always encouraged to substitute your own choices for what we've listed. At the very least you can use it as a shopping list so you don't begin your project missing that one vital component.
First though, a brief rant about static electricity. This is where things may get a little argumentative. First things first, there is no doubt that Electro-static discharge can destroy computer components. Static Electricity is also known as ESD, or that shock you get when you touch the doorknob after walking across the office carpeting.
The question is, how careful do you have to be? Is it necessary to properly ground yourself with an electrostatic wrist strap before touching computer components, or do you just exercise a few simple precautions?
I have to admit I fall on the latter side, but I'm not the only one. Walk into any of those small computer stores you see by the hundred in any city, and go to the back. I'll bet you the guy up to his elbows in computer parts there is not wearing a wrist-strap, most likely because he is also the guy who is going to come out to the front and try to sell you something too. Yet this store will turn out computers as reliable on average as any other computer store you could walk into.
Sure you could say "what about the big manufacturers? What about Dell? Don't their techs wear wrist straps?" I'm sure they do. The thing is, I don't believe that Dell (as one example) has a parts failure rate that is significantly lower than that of any other major or minor manufacturer, and if there is a minor difference, it is going to be because major manufacturers have a standardized quality control system in place that your local AlphaBetaGamma computer store is not going to be able to emulate. With a few simple precautions, I don't think we need to worry much about ESD.
Simple precautions: Build your computer on a hard surface, away from carpets if possible. Wear shoes and a short-sleeved cotton shirt. Synthetic materials like polar fleece are excellent static generators, so it's best to wear natural fibers which don't create little lightning clouds everytime you shift your feet.
Use the anti-static bags that come with most computer components as mats to rest the components on your workspace. If you often get static shocks in your home, it may be a good idea to plug the power cord into your powersupply and turn the switch at the back to the OFF position. You can then touch the metal case of the power supply (or the unpainted metal area of the computer case if the PSU is already mounted) to ground yourself while you work.
Be sure to unplug the power cord from the power supply before connecting any of the power cables to the components, however.
Handling Components Correctly :-
When handling computer components like motherboards, videcards, memory, or even a hard drive it is best to hold them by the edges. If you hold that videocard (for example) by the edges the PCB it is less likely that your fingers will even come in contact with any conductors, decreasing the chance of causing any ESD damage further still.
This is not only a good precaution, it is also a good habit as any Electrical Engineer will tell you. Certain electrical components (namely capacitors) can store an electrical charge even after the power has been disconnected for sometime that can deliver a nasty shock, or kill if they are sufficiently powerful enough... Don't worry though, all the components we'll be installing in the computer are more afraid of you, and don't carry enough charge to cause you harm.
Still, grabbing a board of electronics like you would a sandwich puts your fingers in direct contact with the little metal leads from soldered-on electrical components. If for example, your finger came in contact with the leads from a powerful enough charged capacitor you could get a very strong shock. The opposite rings true if you happen to grab a video card when you're all charged up with static electricity. Instead of receiving a nasty arm-zapping shock, you may just deliver a nasty bolt of static electricity to a sensitive microchip - damaging it in the process.
Obvious precautions:-

Try not to remove articles of clothing while you work on the computer, for esthetic as well as practical reasons. DO NOT let your cat near the computer parts. Cats are walking static death bombs.
Now that the ESD precautions are out of the way, what do you need to build your computer?

- ATX computer case with at least 300-watt power supply
- Intel or AMD processor with appropriate heat sink
- Computer motherboard compatible with your processor
- 1 or more sticks of RAM (memory) compatible with the motherboard and processor
- 1 or more IDE hard disk drives
- 1 or more optical (CD) drives
- 1 floppy disk drive
- 1 PS/2 or USB keyboard.
- 1 PS/2 or USB mouse
- AGP video card (ie. 4XAGP, 8XAGP, etc.) compatible with the motherboard (this may be integrated into the motherboard on some models)
- VGA monitor (computer screen)
- Sound card (these are generally integrated into the motherboard, though depending on your requirements, this may not be enough)
- 10/100 Ethernet Network Adaptor aka NIC (if you plan to connect the computer to other computers in your household)
- A Phillips-head screwdriver with a long neck, preferably magnetized, because you WILL lose a screw or two during the course of this.
- A flashlight is always a good thing to have. So is a big desk, or table where scratches on the surface aren't a big deal.
Remember, you can also peek at the PCstats ShoppingList if you need some current suggestions to this basic list of components.
The system I am going to assemble in the article is a fairly typical Pentium 4 based midrange system for office use. Nothing too cheap, but nothing too expensive either.

Building the computer, first steps :-
Step 1: Preparing the case.
Remove the empty computer case from its packaging. Unscrew and remove both side panels, and take out any items that may be inside. Lay the case down flat on your workspace, so that the mounting space for the motherboard is facing up (see pic 1).

Step 2: Installing motherboard risers.
You need to determine if the case has the appropriate risers installed. Risers, or spacers, keep the motherboard from touching the metal surfaces of the case after it is installed, avoiding a short-circuit and a wrecked computer.
Risers are your friends. Any new case will include some form of riser, metal or plastic. See the picture below for typical examples. They may or may not be pre-installed into the case.

Remove your motherboard from its packaging and lower it into the case.
Installing the Motherboard, CPU :-
Line up the ports on the motherboard (PS/2, USB, etc.) with the appropriate holes in the back panel I/O shield of the case (see pic below)

Once the board is temporarily in place, observe which screw holes in the case line up with the holes in the motherboard. These are where you will need to place risers if they are not already pre-installed. Remove the motherboard and insert the risers in the appropriate screw holes.
Step 3: Installing the CPU :-
Place your motherboard flat on top of the anti-static bag it came in. Ensure that the lever on the cpu-socket is upright (open). Holding the CPU gently on the sides with thumb and fingers, lower it into the socket, ensuring that the arrow on the CPU matches the arrow indented into the socket (see pic below). The processor is keyed to fit into the socket a certain way, and only that way.

Very little effort should be required to insert the CPU in the socket. If you cannot get the CPU to sit evenly DO NOT force it. Remove it completely and try again. Ensure that the CPU is sitting flush with the socket on all sides. No pins should be visible. Once you are sure the CPU is correctly seated in the socket, lower the lever until it locks. This will require a small amount of force.
Note: These instructions will work for any recent CPU/motherboard combination. The orientation of the CPU may be different, but the method of inserting it is the same for older socket chips; whether they be Intel, AMD or VIA processors. This guide does not cover slot-based processors, as they are no longer
Attaching the Heat sink :-
Step 4: Installing the heat sink and cooling fan (socket 478) :-
Cute little guy, aren’t it? German Engineering, so I'm told... Make sure the 2 levers on the top of the heat sink are in their default-unlocked position. Since Intel processors come with a heat sink, installation is pretty straightforward. Even things like thermal interface materials (pastes, pads, or goo's) are already pre-applied for you.

Lower the heat sink gently into the plastic frame around the processor so that the heat sink metal sits evenly on all sides. Push down on the plastic top of the heat sink until the hooks on each side lock into the heat sink retention mechanism frame on the motherboard. This will require some force. Holding one side of the heat sink securely, pull the lever on the other side over until it locks. Again, this will require some force.
Repeat the procedure for the other lever. Consult your motherboard manual for the locations of the three-pin fan headers. There should be one close to the CPU socket. Plug the fan power cord into that header.
Don't choose a fan header at random; make sure the heat sinks' fan is being powered by the correct header for this purpose. If you get the wrong one, there is a chance the fan may shut off when the computer is in suspended mode - meaning the processor will overheat.
There are many different types of after-market heat sinks for both the Intel Pentium 4 and AMD Athlon processors. We're only covering the installation of the stock Intel heat sink, but the basic principle for installing after-market coolers is the same. Some heat sinks may come with a small package of white silicon-based thermal compound, which needs to be applied before the heat sink is installed. If this is the case, only use a very small amount, and spread it over the processor's core only. The thermal compound is only used as an interface between the bottom of the heat sink, and the portion of the processor, which it comes in contact with.
Some thermal compounds are made with conductive metals to achieve better thermal conductivity between the heat sink and processor. If you decide to try these types of Thermal Interface Materials (TIM) out, be sure you clean the surface of the processor and base of the heat sink with a soft cloth and Methyl alcohol gently before applying a small amount of the material. Silver-based TIMs are conductive; so do not get them on any electrical components!

Installing RAM Memory :-
Step 5: Installing RAM :-
All modern RAM (memory) is keyed so it can only fit into the DIMM slots a certain way. With modern motherboards, it should not matter which slot you use, though if they are numbered in the manual or on the board, it is always a good idea to go with slot one first. Hold the RAM module next to the slot so that the indentation(s) on the green PCB line up with the bumps in the slot. (see pic below).

Once you are certain of the orientation of your RAM, open the levers on either side of the DIMM slot and push the RAM module straight down into the slot until both levers snap closed on either side. This will require some force. If it does not seem to be going in with a moderate amount of force, remove the module and re-insert it, making sure that it is exactly lined up with the keyed points in the slot.

Installed properly, the levers on the sides of the DIMM slots will be completely closed and locked into small cutouts on the outer edges of the RAM module.

Mounting the Motherboard :-

Step 6: Installing the Motherboard :-

Ensure that the motherboard mounting area in the case is free of obstructions and that all necessary risers have been installed in the right spots. If there is an extra riser that does not line up with a hole in the motherboard, make sure you remove it. Lower the board into the case as in step 2. Screw the motherboard into the risers. Note that some forms of risers will not require screws to be used. You can figure it out. Once the board has been securely attached, plug in the 20-pin main ATX power connector (see pic).

If you are installing an Intel Pentium 4 machine, you will probably be required to connect one or two extra power connectors (see pic).

Plug the 4-pin 12V auxiliary power, and 6-pin power connectors in also. Note: some motherboards may not require the 6-pin connector at all.
Consult your motherboard manual for the correct locations of the 'front panel' power and reset button wires, the power and hard-drive LED wires and the speaker. Note that the power and hard-drive LED wires are sensitive to polarity, so they will only work one way around. In theory, positive and negative will be indicated on the board and the plugs... In practice, doubtful, so... trial and error. You will not cause any damage if you get it wrong, though, the LEDs will just not light up.
Adding a Hard Drive :-
Step 7: Installing the hard-drive :-
First, we need to ensure that the hard drive is set up to be the master drive on its IDE cable. Each IDE cable can support up to two IDE devices, such as hard-drives, CD-drives, Zip Drives, etc., but in order for this to work, one IDE device must be designated as a master device, and one must be designated as a slave device. You cannot have two master devices or two slave devices on a single cable.

Examine the top of your hard-drive. There should be a chart there depicting the necessary jumper settings to make the drive a master or slave device. Otherwise, the chart will be somewhere on the body of the drive. The set of jumpers will be on the back end of the drive.

Ensure that they are set correctly to enable the drive as a master. You may need a set of tweezers to move the jumpers around if you have been biting your fingernails.
Insert the hard drive into the 3.5" drive-tray and screw it in securely on both sides. Note that hard-drives generally use a different sized screw than CD-ROMs and floppy drives for some completely inexplicable reason.

Hard Drives and Cables
Attach the Molex power cable to the drive. Unlike the floppy drive power plug, these Molex connectors can only fit into the drive one way, so relax, you can't make a mistake here.

Attach the Primary IDE cable to the drive (for any recent motherboard, this should be a 80 wire UDMA cable). It will be keyed to only fit in one way, but to make sure, the red or blue on the cable should be facing the hard-drive power cable.

Attach the long end of the cable to the IDE 0 connector on the motherboard first, then if there are other drives attach those IDE cables to the IDE 1 connector. Serial ATA drives are still fairly new, so we will only cover them briefly.
The Serial ATA cable is keyed to fit into the SATA motherboard header, and hard drive in a certain orientation. It is impossible to attach the Serial ATA cables backwards, and since there is only one hard drive per cable we don't need to worry about the master/slave settings of IDE hard drives.
Serial ATA and IDE are not compatible, so to use SATA hard drives the motherboard must have SATA headers. Some motherboards may come with SATA-to-IDE adaptors, but again the motherboard still must have one SATA header per drive.
The SATA hard drive will require either a 15-pin SATA power connector, or standard 4-pin Molex power connector as we described previously.

Adding a CDROM :-

Step 8: Installing optical (CD) drive :-
Ensure that at least one full sized 5.25" bay is open in the case. Examine the jumper settings on the top of the drive, as you did with the hard-drive. Ensure that the drive is set to 'master'. If your case came with rails, screw them to the sides of the CD drive and insert it into the front of the case until it clicks into place.
Otherwise, slide the drive into the front of the computer until the faceplate of the drive is flush with the front bezel of the case and the screw holes along the side of the drive line up with the case. Then, screw it in securely on both sides. Attach the power cable (same as the hard-drive power cable) to the drive. Attach your secondary IDE cable to the drive. Note that generally this should be a regular 40-wire IDE cable, not the 80-wire UDMA IDE cable that is used for the hard-drive. Some DVD drives will use the 80-wire cable, however. See the picture below for a comparison of the two IDE cable types.

The drive should be keyed, so the cable will only fit one way, but note that the red stripe on the IDE cable should be facing the CD power cable.

Attach the long end of the cable to the 'IDE1' or 'IDE2' connector on the motherboard.
Getting Sound from a CDROM :-

In order to get sound out of the CDROM when playing CD's, we need to attach a special cable between the CDROM and motherboard/soundcard. The CDROM should come with this thin 4-pin cable with flat connectors at either end. If not, be sure to pick one up from the store.

This is the analog audio cable, which needs to be connected between the CD drive and your soundcard (or the motherboard if your soundcard is integrated into the board.). This allows Audio CDs to be directly played from your CD-ROM like an audio CD player. Plug the cable from the connector at the back of the CD drive to the 'audio-in' connector on your soundcard or motherboard. The soundcard connector should be fairly obvious, check your manual for the location of the one on your motherboard.
Step 9: Installing the video card :-

For an AGP video card: The AGP port is the brown slot at the top of the row of peripheral (PCI) slots that runs down the board. Ensure that the catch (AGP Retention Mechanism) at the far end of the port is open, if it is present.

Insert the card firmly into the AGP slot. It should settle evenly, with just a tiny fraction of the gold traces at the bottom of the card visible. Screw the card into the expansion bracket.
For a PCI video card: PCI ports are the white slots running in a row down the rear edge of the board. Which port you choose is fairly irrelevant, though with modern video cards, it is always a good idea to leave the slot below the one you install the card in empty to aid in ventilation of heat. Simply insert the card firmly into the slot. It should sit evenly once inserted, with only a fraction of the gold traces on the bottom of the card visible. Screw the card into the expansion bracket.
Adding an Expansion Card :-

Step 10: Installing PCI expansion cards :-

All PCI cards are physically installed the same way. With modern motherboards, which slots you decide to use should not matter, but it is a good idea to space your expansion cards out in order to help with case ventilation. Simply insert the card firmly into an empty PCI slot. It should sit evenly once inserted, with only a fraction of the gold traces on the bottom of the card visible.

Screw the card into the expansion bracket.

Step 11: Finishing up
If your motherboard came with any extras, such as Modem or network adaptor riser cards, or additional USB ports on a mounting bracket, now's the time to plug them into the board (consult your manual for the correct locations) and screw them into any free mounting brackets you may have.
Double-check all the wiring. Make sure all connections are firmly attached, and ensure that no wires are running close to the top of the CPU heat sink fan. You do NOT want to jam the CPU heat sink fan, especially with an AMD processor.
Double-check everything again. Now get all those loose screws out.

Step 12: Powering up for the first time :-

Stand the case upright, if it is not already. Ensure that no wires are touching the CPU heat sink fan. Plug your monitor cable into the video card (VGA) port, and turn on the monitor. Plug your PS/2 (or USB) keyboard cable into the keyboard port. Plug in the power cord and switch the power supply switch to the on (|) position. Press the power button. Suspense.... sparks?
If everything is connected, as it should be, all system fans should start spinning, you should hear a single beep, and after about 5-10 seconds, the amber light on the monitor should go green, and you will see the computer start to boot.
Depending on the manufacturer of the Motherboard, you may get a splash screen, or just a memory check. The system will then halt with an error because we have yet to install an operation system. If something has gone horribly wrong, just go straight down to the troubleshooting section. If something is on fire, go to the kitchen. You do have an extinguisher, right?
Now check the front LEDs to see if you plugged them in correctly. Power off and fix the LEDS because you didn't. Test the reset button. Assuming you have got to this point without any problems, put the side panels back on, plug in your mouse and network cables and pop your favorite operating system into the CD drive, then power the system back up again. You are done assembling the computer!

Troubleshooting :-

The Troubleshooting section here is not intended as a comprehensive guide to troubleshooting computer systems, but rather as a quick checklist to point you in the right direction.
OK, something has gone wrong. Let's run down the list of possibilities.

If you hit the power button and nothing happened:
Is the power cord plugged in? Is it plugged in the other end too? Check the switch at the back of the case. Make sure that you connected the wire from the case power button to the right connector on the motherboard. Make sure the power connector to the motherboard is in correctly. Check the floppy power cable. Double-check all connections. You did use the risers, right?
If none of this makes a difference, next step is to unplug everything from the motherboard with the exception of the power cable, power button wire, video card, memory and processor. If it still will not power up, it's likely that you have one or more defective components. The most likely culprits are the motherboard or the case power supply.

If the system turns on, but does not beep or begin to boot up:

First, double check all connections and try again. Otherwise, the best thing to do in this circumstance is to unplug everything from the motherboard with the exception of the power button wire, video card, memory and processor, then test it again.
If the computer successfully starts at this point, power off and reconnect one component at a time until you find the problem. If you cannot get it to boot up successfully, it is likely that you have one or more defective parts.

System turns on, beeps intermittently, does not boot up:

Check that your memory (RAM) chip is installed correctly. Remove it and re-install it if necessary.
System turns on, gives a sequence of quick beeps, does not boot up:

Check that your video card is correctly seated in its AGP or PCI slot. The AGP slot especially can be unforgiving of a card that is a tiny bit out of position.
There are a number of other error codes indicated by patterns of beeps from the motherboard speaker, but the two above are the most commonly encountered. If you have got the system up and running, but are experiencing some problems installing an operating system, here are a couple of common issues:

Your system freezes intermittently while installing the OS: -

Could well be a heat issue, especially with AMD processors or older Intel ones. Check that the heat sink fan is spinning and that the heat sink itself is firmly mounted and parallel to the surface of the processor. Assuming you are using a stock heat sink from the manufacturer of the processor, it should be more than adequate to cool the system if properly applied.

You are having problems fully installing the OS due to errors copying files and blue screens:
Errors while copying the setup files, especially with Windows 2000 or XP, are a common indicator of problems with your memory (RAM). It's possible it could also be a hard-drive problem, but if you are getting blue-screens also, especially any ones indicating that a 'page-fault' has occurred, it's time to pop the memory out and haul it back to the store to be tested. And don't leave it there for the night either.

Computer Error Beep Codes :-
_

When the computer makes those funny sounds via the system speaker, it's not doing it because it wants to be heard. The computer is trying to talk to the operator/technician and tell them what's wrong. In testing computer components on and off for the last three to four years, I find that almost all motherboards adhere to the IBM BIOS standard beep codes... I think a few OEM's have developed their own or use Phoenix or AMI beep codes, but for the most part motherboard manufacturers uses the IBM based ones because they are grand fathered in.

Beep Code: Description of Problem:
No Beeps Short, No power, Bad CPU/MB, Loose Peripherals
One Beep Everything is normal and Computer Posted fine
Two Beeps POST/CMOS Error
One Long Beep, One Short Beep Motherboard Problem
One Long Beep, Two Short Beeps Video Problem
One Long Beep, Three Short Beeps Video Problem
Three Long Beeps Keyboard Error
Repeated Long Beeps Memory Error
Continuous Hi-Lo Beeps CPU Overheating

So as you can see, if your computer doesn't start up and starts beeping away like a mime you can start the process of figuring out what is wrong by stopping for a second and listening. From a single beep which tells you everything is okay, to three long beeps which indicate a keyboard error to the siren like Hi-Lo beeps that tell you the CPU is overheating - listening to your computer is good!

IP Addressing

2009-12-02T02:47:00.000-08:00

An IP (Internet Protocol) address is a unique identifier for a node or host connection on an IP network. An IP address is a 32 bit binary number usually represented as 4 decimal values, each representing 8 bits, in the range 0 to 255 (known as octets) separated by decimal points. This is known as "dotted decimal" notation.

Example: 140.179.220.200

It is sometimes useful to view the values in their binary form.

140     .179     .220     .200

10001100.10110011.11011100.11001000

Every IP address consists of two parts, one identifying the network and one identifying the node. The Class of the address and the subnet mask determine which part belongs to the network address and which part belongs to the node address.

Address Classes

There are 5 different address classes. You can determine which class any IP address is in by examining the first 4 bits of the IP address.

Class A addresses begin with 0xxx, or 1 to 126 decimal.
Class B addresses begin with 10xx, or 128 to 191 decimal.
Class C addresses begin with 110x, or 192 to 223 decimal.
Class D addresses begin with 1110, or 224 to 239 decimal.
Class E addresses begin with 1111, or 240 to 254 decimal.

Addresses beginning with 01111111, or 127 decimal, are reserved for loopback and for internal testing on a local machine. [You can test this: you should always be able to ping 127.0.0.1, which points to yourself] Class D addresses are reserved for multicasting. Class E addresses are reserved for future use. They should not be used for host addresses.

Now we can see how the Class determines, by default, which part of the IP address belongs to the network (N) and which part belongs to the node (n).

Class A -- NNNNNNNN.nnnnnnnn.nnnnnnn.nnnnnnn
Class B -- NNNNNNNN.NNNNNNNN.nnnnnnnn.nnnnnnnn
Class C -- NNNNNNNN.NNNNNNNN.NNNNNNNN.nnnnnnnn

In the example, 140.179.220.200 is a Class B address so by default the Network part of the address (also known as the Network Address) is defined by the first two octets (140.179.x.x) and the node part is defined by the last 2 octets (x.x.220.200).

In order to specify the network address for a given IP address, the node section is set to all "0"s. In our example, 140.179.0.0 specifies the network address for 140.179.220.200. When the node section is set to all "1"s, it specifies a broadcast that is sent to all hosts on the network. 140.179.255.255 specifies the example broadcast address. Note that this is true regardless of the length of the node section.

Private Subnets

There are three IP network addresses reserved for private networks. The addresses are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They can be used by anyone setting up internal IP networks, such as a lab or home LAN behind a NAT or proxy server or a router. It is always safe to use these because routers on the Internet will never forward packets coming from these addresses. These addresses are defined in RFC 1918.

Subnetting an IP Network can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic. In an Ethernet network, all nodes on a segment see all the packets transmitted by all the other nodes on that segment. Performance can be adversely affected under heavy traffic loads, due to collisions and the resulting retransmissions. A router is used to connect IP networks to minimize the amount of traffic each segment must receive.

Subnet Masking

Applying a subnet mask to an IP address allows you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. Performing a bitwise Logical AND operation between the IP address and the subnet mask results in the Network Address or Number.
For example, using our test IP address and the default Class B subnet mask, we get:

10001100.10110011.11110000.11001000      140.179.240.200   Class B IP Address

11111111.11111111.00000000.00000000      255.255.000.000   Default Class B Subnet Mask

--------------------------------------------------------

10001100.10110011.00000000.00000000      140.179.000.000   Network Address

Default subnet masks:

Class A - 255.0.0.0 - 11111111.00000000.00000000.00000000
Class B - 255.255.0.0 - 11111111.11111111.00000000.00000000
Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000

Additional bits can be added to the default subnet mask for a given Class to further subnet, or break down, a network. When a bitwise LOGICAL AND operation is performed between the subnet mask and IP address, the result defines the Subnet Address (also called the Network Address or Network Number). There are some restrict

ions on the subnet address. Node addresses of all "0"s and all "1"s are reserved for specifying the local network (when a host does not know its network address) and all hosts on the network (broadcast address), respectively. This also applies to subnets. A subnet address cannot be all "0"s or all "1"s. This also implies that a 1 bit subnet mask is not allowed. This restriction is required because older standards enforced this restriction. Recent standards that allow use of these subnets have superceded these standards, but many "legacy" devices do not support the newer standards. If you are operating in a controlled environment, such as a lab, you can safely use these restricted subnets.

To calculate the number of subnets or nodes, use the formula (2ⁿ-2) where n = number of bits in either field, and 2ⁿ represents 2 raised to the nth power. Multiplying the number of subnets by the number of nodes available per subnet gives you the total number of nodes available for your class and subnet mask. Also, note that although subnet masks with non-contiguous mask bits are allowed, they are not recommended.

Example:

10001100.10110011.11011100.11001000      140.179.220.200   IP Address

11111111.11111111.11100000.00000000      255.255.224.000   Subnet Mask

--------------------------------------------------------

10001100.10110011.11000000.00000000      140.179.192.000   Subnet Address

10001100.10110011.11011111.11111111      140.179.223.255   Broadcast Address

In this example a 3 bit subnet mask was used. There are 6 (2³-2) subnets available with this size mask (remember that subnets with all 0's and all 1's are not allowed). Each subnet has 8190 (2¹³-2) nodes. Each subnet can have nodes assigned to any address between the Subnet address and the Broadcast address. This gives a total of 49,140 nodes for the entire class B address subnetted this way. Notice that this is less than the 65,534 nodes an unsubnetted class B address would have.

You can calculate the Subnet Address by performing a bitwise LOGICAL AND operation between the IP address and the subnet mask, then setting all the host bits to 0s. Similarly, you can calculate the Broadcast Address for a subnet by performing the same LOGICAL AND between the IP address and the subnet mask, then setting all the host bits to 1s. That is how these numbers are derived in the example above.

Subnetting always reduces the number of possible nodes for a given network. There are complete subnet tables available here for CLASS A , B, C . These tables list all the possible subnet masks for each class, along with calculations of the number of networks, nodes and total hosts for each subnet.

Here is another, more detailed, example. Say you are assigned a Class C network number of 200.133.175.0 (apologies to anyone who may actually own this domain address). You want to utilize this network across multiple small groups within an organization. You can do this by subnetting that network with a subnet address.

We will break this network into 14 subnets of 14 nodes each. This will limit us to 196 nodes on the network instead of the 254 we would have without subnetting, but gives us the advantages of traffic isolation and security. To accomplish this, we need to use a subnet mask 4 bits long.
Recall that the default Class C subnet mask is

255.255.255.0 (11111111.11111111.11111111.00000000 binary)

Extending this by 4 bits yields a mask of

255.255.255.240 (11111111.11111111.11111111.11110000 binary)

This gives us 16 possible network numbers, 2 of which cannot be used:

Subnet bits	Network Number	Node Addresses	Broadcast Address
0000	200.133.175.0	Reserved	None
0001	200.133.175.16	.17 thru .30	200.133.175.31
0010	200.133.175.32	.33 thru .46	200.133.175.47
0011	200.133.175.48	.49 thru .62	200.133.175.63
0100	200.133.175.64	.65 thru .78	200.133.175.79
0101	200.133.175.80	.81 thru .94	200.133.175.95
0110	200.133.175.96	.97 thru .110	200.133.175.111
0111	200.133.175.112	.113 thru .126	200.133.175.127
1000	200.133.175.128	.129 thru .142	200.133.175.143
1001	200.133.175.144	.145 thru .158	200.133.175.159
1010	200.133.175.160	.161 thru .174	200.133.175.175
1011	200.133.175.176	.177 thru .190	200.133.175.191
1100	200.133.175.192	.193 thru .206	200.133.175.207
1101	200.133.175.208	.209 thru .222	200.133.175.223
1110	200.133.175.224	.225 thru .238	200.133.175.239
1111	200.133.175.240	Reserved	None

Now that you understand "classful" IP Subnetting principals, you can forget them ;). The reason is CIDR -- Classless InterDomain Routing. CIDR was invented several years ago to keep the internet from running out of IP addresses. The "classful" system of allocating IP addresses can be very wasteful; anyone who could reasonably show a need for more that 254 host addresses was given a Class B address block of 65533 host addresses. Even more wasteful were companies and organizations that were allocated Class A address blocks, which contain over 16 Million host addresses! Only a tiny percentage of the allocated Class A and Class B address space has ever been actually assigned to a host computer on the Internet.

People realized that addresses could be conserved if the class system was eliminated. By accurately allocating only the amount of address space that was actually needed, the address space crisis could be avoided for many years. This was first proposed in 1992 as a scheme called Supernetting. Under supernetting, the classful subnet masks are extended so that a network address and subnet mask could, for example, specify multiple Class C subnets with one address. For example, If I needed about 1000 addresses, I could supernet 4 Class C networks together:

192.60.128.0   (11000000.00111100.10000000.00000000)  Class C subnet address

192.60.129.0   (11000000.00111100.10000001.00000000)  Class C subnet address

192.60.130.0   (11000000.00111100.10000010.00000000)  Class C subnet address

192.60.131.0   (11000000.00111100.10000011.00000000)  Class C subnet address

--------------------------------------------------------

192.60.128.0   (11000000.00111100.10000000.00000000)  Supernetted Subnet address

255.255.252.0  (11111111.11111111.11111100.00000000)  Subnet Mask

192.60.131.255 (11000000.00111100.10000011.11111111)  Broadcast address

In this example, the subnet 192.60.128.0 includes all the addresses from 192.60.128.0 to 192.60.131.255. As you can see in the binary representation of the subnet mask, the Network portion of the address is 22 bits long, and the host portion is 10 bits long.

Under CIDR, the subnet mask notation is reduced to a simplified shorthand. Instead of spelling out the bits of the subnet mask, it is simply listed as the number of 1s bits that start the mask. In the above example, instead of writing the address and subnet mask as

192.60.128.0, Subnet Mask 255.255.252.0

the network address would be written simply as:

192.60.128.0/22

which indicates starting address of the network, and number of 1s bits (22) in the network portion of the address. If you look at the subnet mask in binary (11111111.11111111.11111100.00000000), you can easily see how this notation works.

The use of a CIDR notated address is the same as for a Classful address. Classful addresses can easily be written in CIDR notation (Class A = /8, Class B = /16, and Class C = /24)

It is currently almost impossible for an individual or company to be allocated their own IP address blocks. You will simply be told to get them from your ISP. The reason for this is the ever-growing size of the internet routing table. Just 10 years ago, there were less than 5000 network routes in the entire Internet. Today, there are over 100,000. Using CIDR, the biggest ISPs are allocated large chunks of address space (usually with a subnet mask of /19 or even smaller); the ISP's customers (often other, smaller ISPs) are then allocated networks from the big ISP's pool. That way, all the big ISP's customers (and their customers, and so on) are accessible via 1 network route on the Internet. But I digress.

It is expected that CIDR will keep the Internet happily in IP addresses for the next few years at least. After that, IPv6, with 128 bit addresses, will be needed. Under IPv6, even sloppy address allocation would comfortably allow a billion unique IP addresses for every person on earth! The complete and gory details of CIDR are documented in RFC1519, which was released in September of 1993.

bits	Subnet Mask	CIDR	# Subnets	# Hosts	*Nets Hosts**
2	255.192.0.0	/10	2	4194302	8388604
3	255.224.0.0	/11	6	2097150	12582900
4	255.240.0.0	/12	14	1048574	14680036
5	255.248.0.0	/13	30	524286	15728580
6	255.252.0.0	/14	62	262142	16252804
7	255.254.0.0	/15	126	131070	16514820
8	255.255.0.0	/16	254	65534	16645636
9	255.255.128.0	/17	510	32766	16710660
10	255.255.192.0	/18	1022	16382	16742404
11	255.255.224.0	/19	2046	8190	16756740
12	255.255.240.0	/20	4094	4094	16760836
13	255.255.248.0	/21	8190	2046	16756740
14	255.255.252.0	/22	16382	1022	16742404
15	255.255.254.0	/23	32766	510	16710660
16	255.255.255.0	/24	65534	254	16645636
17	255.255.255.128	/25	131070	126	16514820
18	255.255.255.192	/26	262142	62	16252804
19	255.255.255.224	/27	524286	30	15728580
20	255.255.255.240	/28	1048574	14	14680036
21	255.255.255.248	/29	2097150	6	12582900
22	255.255.255.252	/30	4194302	2	8388604

# bits	Subnet Mask	CIDR	# Subnets	# Hosts	*Nets Hosts**
2	255.255.192.0	/18	2	16382	32764
3	255.255.224.0	/19	6	8190	49140
4	255.255.240.0	/20	14	4094	57316
5	255.255.248.0	/21	30	2046	61380
6	255.255.252.0	/22	62	1022	63364
7	255.255.254.0	/23	126	510	64260
8	255.255.255.0	/24	254	254	64516
9	255.255.255.128	/25	510	126	64260
10	255.255.255.192	/26	1022	62	63364
11	255.255.255.224	/27	2046	30	61380
12	255.255.255.240	/28	4094	14	57316
13	255.255.255.248	/29	8190	6	49140
14	255.255.255.252	/30	16382	2	32764

# bits	Subnet Mask	CIDR	# Subnets	# Hosts	*Nets Hosts**
2	255.255.255.192	/26	2	62	124
3	255.255.255.224	/27	6	30	180
4	255.255.255.240	/28	14	14	196
5	255.255.255.248	/29	30	6	180
6	255.255.255.252	/30	62	2	124