From: NSN - CO/Santa Fe de Bogota ("Gutierrez,)
Date: Thu Nov 20 2008 - 20:02:32 ARST
Also if you are using only Cisco equipmente then configure UDLD or
80.3ah, it helps also to prevent loops.
Rodrigo
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
>Behalf Of ext Gutierrez, Rodrigo (NSN - CO/Santa Fe de Bogota)
>Sent: Thursday, November 20, 2008 4:49 PM
>To: Antonio Soares; Kim teu; Cisco certification
>Subject: RE: Layer 2 loop breaks OSPF adjacency over Layer 3 links
>
>Just use broadcast storm control to diminish the loop impact
>processor wise and to define the broadcast threshold allowed
>as per interface, in that way it will give you more time to
>track down the source of the problem or at least time enough
>to disconnect all secondary layer 2 redundancy, loops are
>lethal and can bring down your network in a matter of seconds,
>
>Rodrigo
>
>
>
>
>>-----Original Message-----
>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
>Behalf Of
>>ext Antonio Soares
>>Sent: Thursday, November 20, 2008 4:43 PM
>>To: 'Kim teu'; 'Cisco certification'
>>Subject: RE: Layer 2 loop breaks OSPF adjacency over Layer 3 links
>>
>>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_n
>>ote09186a0080136673.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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