RE: Troubleshooting a suspect L2 loop

as you cann't control the customer side there will be no assurance that thing
like this will not happen. just take correct measures on ur side.

> Subject: Re: Troubleshooting a suspect L2 loop
> To: dr3d3m3nt0_at_gmail.com; ccielab_at_groupstudy.com
> From: robclav_at_gmail.com
> Date: Fri, 19 Aug 2011 07:24:26 +0000
>
> Hi,
> First of all you need to look for what kind of devices are connected to
these ports. If the answer is servers, look for 'teaming'(lacp) problems mixed
with 802.1q.
> By other hand, you should review and control the broadcast rate limit at
these ports, and count, how many mac's are you seeing.
> If you have switches behind, then look for he loop.
> Hth,
> Robclav
>
> Enviado desde mi BlackBerry. de Vodafone
>
> -----Original Message-----
> From: Mad_Prof <dr3d3m3nt0_at_gmail.com>
> Sender: nobody_at_groupstudy.com
> Date: Thu, 18 Aug 2011 21:46:54
> To: <ccielab_at_groupstudy.com>
> Reply-To: Mad_Prof <dr3d3m3nt0_at_gmail.com>
> Subject: Troubleshooting a suspect L2 loop
>
> Hello,
>
> I had an incident this week where a customer' server was misconfigured and
> it was sending out BPDU which resulted in the core switches pegged the cpu
> at 99%.
> The log output showed multiple events involving duplicate ip addresses ,
> specifically the ips of the neighbor core switch and show proc cpu sorted
> showed
> ARP Input at nearly 20%. I managed to fix the issue by shutting down all
the
> ports on one switch , bring the ports back online in groups and check if
the
> cpu levels
> would increase. I found the ports involved in a L2 loop and configured
> spanning-tree guard bpduguard. These ports immediately went into
> err-disable and the cpu came down to about 3%. I managed to fix the problem
> without a completely comprehending how L2 loop comes into existence, how to
> classify the
> type of L2 loop and the correct process to troubleshoot. Any assistance is
> greatly appreciated.
>
>
>
>
> Thanks
> KS
>
>
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Received on Fri Aug 19 2011 - 18:36:19 ART