From: Kim teu (kim.teu@gmail.com)
Date: Thu Nov 20 2008 - 20:30:40 ARST
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 <amsoares@netcabo.pt> 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
>
>
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