STP Loop

[jcleary]

It looks from the logs that there is a loop. Is there any way to track down where it is comng from?

it looks like my g2/5 is the only thing that is the common factor.

Any ideas?

apping between port Gi2/5 and port Gi3/3

Sep 13 06:42:31: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8D:1C in vlan 1 is fl

apping between port Gi2/5 and port Po1

Sep 13 07:52:05: %C4K_EBM-4-HOSTFLAPPING: Host 00:00:79:58:63:E2 in vlan 1 is fl

apping between port Gi2/5 and port Fa4/39

Sep 13 07:59:47: %C4K_EBM-4-HOSTFLAPPING: Host 00:08:74:1F:C1:26 in vlan 1 is fl

apping between port Gi2/5 and port Fa5/32

Sep 13 09:58:03: %C4K_EBM-4-HOSTFLAPPING: Host 00:01:03:BE:94:B0 in vlan 1 is fl

apping between port Gi2/5 and port Gi3/3

Sep 13 11:52:36: %C4K_EBM-4-HOSTFLAPPING: Host 00:07:E9:82:E9:E4 in vlan 1 is fl

apping between port Gi2/5 and port Gi2/3

Sep 13 11:55:48: %C4K_EBM-4-HOSTFLAPPING: Host 00:01:03:BE:94:B0 in vlan 1 is fl

apping between port Gi2/5 and port Gi3/3

Sep 14 06:06:39: %C4K_EBM-4-HOSTFLAPPING: Host 00:00:79:58:63:E2 in vlan 1 is fl

apping between port Gi2/5 and port Fa4/39

Sep 14 06:12:18: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:35:EB:58 in vlan 1 is fl

apping between port Gi2/5 and port Po1

Sep 14 06:15:15: %C4K_EBM-4-HOSTFLAPPING: Host 00:08:74:1F:C1:26 in vlan 1 is fl

apping between port Gi2/5 and port Fa5/32

Sep 14 08:16:07: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8D:1C in vlan 1 is fl

apping between port Po1 and port Gi2/5

Sep 14 21:53:24: %C4K_EBM-4-HOSTFLAPPING: Host 00:00:79:58:86:01 in vlan 1 is fl

apping between port Po1 and port Gi2/5

Sep 14 23:44:44: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8D:1C in vlan 1 is fl

apping between port Gi2/5 and port Po1

Sep 14 23:46:30: %C4K_EBM-4-HOSTFLAPPING: Host 00:01:03:BE:94:B0 in vlan 1 is fl

apping between port Gi2/5 and port Gi3/3

Sep 15 03:03:53: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:C1:EA:FF in vlan 1 is fl

apping between port Gi2/5 and port Po2

Sep 15 03:11:31: %C4K_EBM-4-HOSTFLAPPING: Host 00:00:79:50:23:FF in vlan 1 is fl

apping between port Gi2/5 and port Po1

Sep 15 03:12:31: %C4K_EBM-4-HOSTFLAPPING: Host 00:01:03:BE:94:B0 in vlan 1 is fl

apping between port Gi2/5 and port Gi3/3

Sep 15 03:15:58: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8D:30 in vlan 1 is fl

apping between port Gi2/5 and port Po2

Sep 15 03:17:47: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8D:1C in vlan 1 is fl

apping between port Gi2/5 and port Po1

Sep 15 05:02:10: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:E8:56:C9 in vlan 1 is fl

apping between port Gi2/5 and port Gi3/4

Sep 15 10:14:19: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:47:BF:8E:5B in vlan 1 is fl

apping between port Gi2/5 and port Po1

[mark-obrien]

It doesn't look like a loop, but probably some trunk in the network is bouncing pretty regularly. Each time it goes up or down, STP holds a new root bridge election and/or new paths to the root bridge. As this occurs, various ports will be changed between forwarding and blocking, and hosts may appear to be coming from different directions (ports) after each transition.

You need to go through the trunks in the network to find which one is bouncing.

HTH

Mark

[jcleary]

Will A 4500 log interface updowns by default?

[mark-obrien]

I'm fairly certain it will. I think in your situation, the trunk that is bouncing is not on the switch whose log you posted.

Mark

[jcleary]

I looked in all of my switches and I dont see any bouncing. any other ideas?

[milan.kulik]

Are there any hubs in your network?

Is Bpduguard enabled on user ports?

Have you received any TCN traps in the moment of flapping?

Regards,

Milan

[glen.grant]

We have seen this when the Supervisor is starting to go south and we have replaced a lot of these . Make sure test diags are set to complete and try rebooting switch .

[jcleary]

You have seen a lot of SupIV's go bad? what are test diags?