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Community Member

Flapping problem

hi all,

today every thing was going good at the university where i work in network support, until the following appeared on one 4506 switch

01:56:29: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:00:01 in vlan 1 is flapping

between port Gi1/2 and port Gi6/26

01:56:30: %C4K_EBM-4-HOSTFLAPPING: Host 00:01:2E:08:53:01 in vlan 1 is flapping

between port Gi1/2 and port Gi6/17

01:56:31: %C4K_EBM-4-HOSTFLAPPING: Host 00:02:B3:0B:59:99 in vlan 1 is flapping

between port Gi1/2 and port Gi6/14

01:56:33: %C4K_EBM-4-HOSTFLAPPING: Host AA:00:04:00:32:08 in vlan 1 is flapping

between port Gi1/2 and port Gi6/2

01:56:37: %C4K_EBM-4-HOSTFLAPPING: Host AA:00:04:00:33:08 in vlan 1 is flapping

between port Gi1/2 and port Gi6/27

01:56:38: %C4K_EBM-4-HOSTFLAPPING: Host 00:14:6A:A8:7D:80 in vlan 1 is flapping

between port Gi1/2 and port Gi6/15

01:56:44: %C4K_EBM-4-HOSTFLAPPING: Host 02:01:0A:00:00:01 in vlan 1 is flapping

between port Gi1/2 and port Gi6/26

01:56:46: %C4K_EBM-4-HOSTFLAPPING: Host AA:00:04:00:32:08 in vlan 1 is flapping

between port Gi6/2 and port Gi1/2

01:56:50: %C4K_EBM-4-HOSTFLAPPING: Host 00:15:62:54:88:40 in vlan 1 is flapping

between port Gi1/2 and port Gi6/15

it is not only those lines... it kept going and going with defferent MACs and ports until i unpluged the Gi1/2 wich is the connection between the old campus to the new campus. can any one tell me what is the problem?

also when the problem appeared, all the netowrk in the university was down, we use cisco switches 2950, and 2970 in addition to four 4000 series switches.

when i unpluged the Gi1/2 the problem stop. but some switches still down and are not any more on the network.

?????? any help please.??? it is argent.

2 REPLIES

Re: Flapping problem

Hi

There is a loop in u r network.

Check if u have redundant links between u r switches,and check the STP topology.

Thanks

Mahmood

Community Member

Re: Flapping problem

thank you Mahmood,

but when i elemenate the segment that seems to cause the problem, there are some switches that did not work, i meane; when i unpluged the source of the problem on the root switch, switches on the 1st layer start to work, but the layers after that did not.

for example: assume

RootSwitch ----> SwitchA ----> SwitchB

now RootSwitch can see SwitchA but not SwitchB until i changed the uplink on SwitchB, even though i did not change any configuration on those switches.

any ideas ??

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