Comments for AlwaysTheNetwork

Comment on Studying ITILv3 by Ocansey

Ocansey — Sat, 04 Sep 2010 09:48:48 +0000

I want to study for the Itil v3 test. What useful materials out there that can help me study. Help me.

Comment on %C4K_EBM-4-HOSTFLAPPING by CCIE to be Roger Perkin

CCIE to be Roger Perkin — Thu, 02 Sep 2010 22:55:25 +0000

Thanks for the post – a lot slicker than shutting down every port on the switch and bringing them up one at a time which I have seen done before!

Roger

Comment on %C4K_EBM-4-HOSTFLAPPING by Daniel Gurgel

Daniel Gurgel — Tue, 31 Aug 2010 17:43:47 +0000

In my case, I have VRRP on Linux servers and everything is just a false alarm. To disable logs, do:

logging discriminator MACFLAP msg-body drops flapping
logging buffered discriminator MACFLAP 512000
logging console discriminator MACFLAP
logging monitor discriminator MACFLAP
!
logging host IP discriminator MACFLAP

Comment on BGP Multipath-Relax by Pooja

Pooja — Mon, 30 Aug 2010 04:23:02 +0000

Thanks a lot…I am right now facing exactly the same situaion and this blog of yours helped me to crack it on CPE side…..

However, I am still facing issues on MPLS PEs. Can you let me know from which IOS onwards this command is supported?

Comment on %C4K_EBM-4-HOSTFLAPPING by Adam K-F

Adam K-F — Sat, 28 Aug 2010 02:47:54 +0000

Could have been two different vlan access ports meaning no VLAN tagging was being sent to the unmanaged switch. This would allow inter-vlan traffic.

Comment on %C4K_EBM-4-HOSTFLAPPING by mikeym

mikeym — Sat, 28 Aug 2010 01:53:16 +0000

I surprised. If the workgroup switch is in 2 different vlans how did it creat a loop?

Comment on %C4K_EBM-4-HOSTFLAPPING by Ethan Banks

Ethan Banks — Fri, 27 Aug 2010 15:44:56 +0000

Seen this also during temporary STP convergence events, where a link that was previously blocked, usually a couple of layers downstream, becomes unblocked. Have also seen this in HP bladecenters using virtual connect modules where one is active and one is standby, and the admin is doing a bunch of configuration and/or is testing virtual connect failover. Ditto on those who mentioned a MAC shared between multiple interfaces, a common load-balancing mechanism.

Comment on %C4K_EBM-4-HOSTFLAPPING by wirerat

wirerat — Fri, 27 Aug 2010 11:01:34 +0000

Just dealt with the bonded interface issue yesterday on a 3750. The exact error messages are below.

Aug 26 11:55:56.677: %SW_MATM-4-MACFLAP_NOTIF: Host 0015.170d.9da9 in vlan 1 is flapping between port Gi2/0/21 and port Gi3/0/10
Aug 26 11:56:11.928: %SW_MATM-4-MACFLAP_NOTIF: Host 0015.170d.9da9 in vlan 1 is flapping between port Gi2/0/21 and port Gi3/0/10

Comment on %C4K_EBM-4-HOSTFLAPPING by ZeroZeroFourteen

ZeroZeroFourteen — Fri, 27 Aug 2010 03:43:43 +0000

I may have to correct myself, when the above situation in my comment happens the message I see is MAC FLOP not HOST FLAP.

Could be a variation in console messages among platforms or something different all together, what platform generated these messages?

I have seen the MAC FLOP on 3750′s.

Comment on %C4K_EBM-4-HOSTFLAPPING by ZeroZeroFourteen

ZeroZeroFourteen — Fri, 27 Aug 2010 03:41:23 +0000

This also happens if a server is using a bonded interface (linux) and the switch is not configured for LACP to the server.

As the server load balances, the bond interface mac address appears on more than one physical interface.