Go CCIE Go!! - A Cisco Certified Internetwork Expert

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 >> >> >>Blogs and organic groups at http://www.ccie.net >> >>______________________________________________________________ >_________ >>Subscription information may be found at: >>http://www.groupstudy.com/list/CCIELab.html >> >> >>Blogs and organic groups at http://www.ccie.net >> >>______________________________________________________________ >_________ >>Subscription information may be found at: >>http://www.groupstudy.com/list/CCIELab.html > > >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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