Port Flap

Unanswered Question
Aug 28th, 2007
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I am having C4507 switch. In that I seeing an error saying

Aug 28 13:06:09.787: %C4K_EBM-4-HOSTFLAPPING: Host 00:03:BA:DB:D0:EF in vlan 20

is flapping between port Gi4/30 and port Po30

I have searched in Cisco site and I found no work around. As I am getting this error approx once for a minute can some one please help me to fix this.

Highly appriciated if someone can help asap.


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Jagdeep Gambhir Tue, 08/28/2007 - 05:45
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%C4K_EBM-4-HOSTFLAPPING: Host [mac-addr] in vlan [dec] is flapping between port [char] and

port [char]

Points that the specified host is detected as a source address on multiple ports.

Typically, a host is supposed to be learned on only one port. A spanning tree loop is the

most common cause of this condition. All traffic from the specified host is temporarily

dropped. After 15 seconds, forwarding is reenabled. If the problem persists, the traffic from the problem host continues to be dropped indefinitely.

Recommended Action: Make sure that spanning tree is enabled to prevent spanning tree

loops. If you have spanning tree disabled, make sure that you have no spanning tree loops

in your network.



cisconoval Tue, 08/28/2007 - 05:50
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Thanks for your reply.

I have checked the Spanning Tree which is running. Still I am getting the same error.


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