Layer 2 loop breaks OSPF adjacency over Layer 3 links

November 20, 2008 @ 3:09 pm · Filed under CCIE Study

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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