Go CCIE Go!! - A Cisco Certified Internetwork Expert

THANKS. You are right. The loop brought down the entire data center because of the loss of OSPF adjacency. I had to go there personally to break the loop…
I did found the problem. I removed the “channel-group 12 mode on” command on one switch, but forgot to remove it from the partner switch…
Regards, Kim
On Thu, Nov 20, 2008 at 3:42 PM, Antonio Soares wrote:
> A STP Loop can stop everything in your network. I saw an entire data center > going down in less than 1 second! When this is > happening, the best to do is to break every existent L2 redundant link > quickly. In some situations, if you don’t have physical > access to the equipments, this is just not possible! > > Then when the storm is over, you can try to trace the source of the > problem. But i can tell you it’s very difficult or even not > possible to find out what failed. > > Cisco has a good document about this: > > > http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080136673.shtml > > > > Regards, > > Antonio Soares, CCIE #18473 (R&S) > amsoares@netcabo.pt > > —–Original Message—– > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of > Kim teu > Sent: quinta-feira, 20 de Novembro de 2008 14:55 > To: Cisco certification > Subject: Layer 2 loop breaks OSPF adjacency over Layer 3 links > > Hello all, > > *Has anyone experienced a layer 2 loop event that caused OSPF adjacency to > be dropped for layer 3 links? Any idea why?* > > > ** > > *What’s the best way to diagnose the cause of the layer 2 after the outage? > The following is what I see in the log.** VLAN 56 is looping…* > > > *The switch is seeing packet sourced from itself::* > > >>>472825: .Nov 19 15:38:56 CST: %STANDBY-3-DUPADDR: Duplicate address > 192.168.97.1 on Vlan56, sourced by 0017.df1c.6800 > > > > *The standby state change to active because the switch lost it connection > to the active switch because of SPT loop prevention::* > > >>>472826: .Nov 19 15:39:00 CST: %STANDBY-6-STATECHANGE: Vlan72 Group 72 > state Standby -> Active > > >>>472827: .Nov 19 15:39:03 CST: %STANDBY-6-STATECHANGE: Vlan116 Group > >>>116 > state Standby -> Active > > >>>472828: .Nov 19 15:39:26 CST: %STANDBY-3-DUPADDR: Duplicate address > 192.168.97.1 on Vlan56, sourced by 0017.df1c.6800 > > >>>472829: .Nov 19 15:39:38 CST: %STANDBY-6-STATECHANGE: Vlan152 Group > >>>152 > state Active -> Speak > > >>>472830: .Nov 19 15:39:47 CST: %OSPF-5-ADJCHG: Process 10, Nbr > 192.168.200.5 on Vlan704 from EXSTART to DOWN, Neighbor Down: Dead timer > expired > > >>>472831: .Nov 19 15:39:54 CST: %STANDBY-6-STATECHANGE: Vlan134 Group > >>>134 > state Active -> Speak > > >>>472832: .Nov 19 15:39:56 CST: %STANDBY-3-DUPADDR: Duplicate address > 192.168.97.1 on Vlan56, sourced by 0017.df1c.6800 > > >>>472833: .Nov 19 15:39:59 CST: %STANDBY-6-STATECHANGE: Vlan152 Group > >>>152 > state Standby -> Active > >>>472834: .Nov 19 15:40:14 CST: %STANDBY-6-STATECHANGE: Vlan134 Group > >>>134 > state Standby -> Active > > > Kim > > > Blogs and organic groups at http://www.ccie.net > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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