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New Member

Can anyone confirm this error on our 4006

flapping between port 2/35 and port 1/1

2003 Jun 25 06:19:08 %SYS-4-P2_WARN: 1/Host 00:03:47:17:6a:57 is flapping betwee

n port 2/35 and port 2/15

2003 Jun 25 06:19:09 %SYS-4-P2_WARN: 1/Host 00:60:b0:43:f5:66 is flapping betwee

n port 2/35 and port 2/36

2003 Jun 25 06:19:11 %SYS-4-P2_WARN: 1/Host 00:20:4a:52:69:17 is flapping betwee

n port 2/35 and port 2/34

2003 Jun 25 06:19:11 %SYS-4-P2_WARN: 1/Host 00:02:b3:89:df:a8 is flapping betwee

n port 2/35 and port 3/4

2003 Jun 25 06:19:14 %SYS-4-P2_WARN: 1/Host 00:0b:cd:9a:fd:f7 is flapping betwee

n port 2/35 and port 3/10

If we disconnect a gig connection to one of out other buildings the errors go away. The other building has 2950 switches with shared hubs off those. There are no loops in the network so I don't know how this could be a spannign tree issues.

The 4006 is pretty much un-usable when we connect the suspect building back in.

Any insites would be helpful.


Re: Can anyone confirm this error on our 4006

Reference the following link:

. %SYS-4-P2_WARN: Host [mac addr] is flapping between port [dec/dec] and port [dec/dec]

The above message indicates that your Catalyst 4000 switch has learned a MAC address that already exists in its CAM table on a port other than the original one.

Recommended Action: What you need to do is to track down how this MAC address was learned from both ports.

Step 1: Consider port the first port. Issue the show cam dynamic [port] command. If you see the MAC address 00:50:0f:20:08:00 coming out in the list of the MAC addresses learned on this port, try to see if this is a single host that is connected or if there are multiple hosts registered on that port.

Step 2: If it is a single host that is connected, check the other port that is registered and see if the host is dually attached to the switch. If however, the host has connections to other devices that can eventually lead back into this switch, try to track down the intermediate devices that are in between.

Note: The best way to achieve this (assuming that they are Cisco devices) is to use the output of the command show cdp neighbors detail.




Re: Can anyone confirm this error on our 4006

port 2/35 seems to be in common. Is that the link to the other building? Track down whats on a pair of these flapping ports. Are there any wireless devices that may be roaming or wireless bridges that may be overlapping? If both offices have wireless access points they may be creating a bridge you are not aware of.

New Member

Re: Can anyone confirm this error on our 4006

Well, you might have a faulty 2950. You might want to restart. If that doesn't fix your problem, then replace it if at all possible. I have also had the same problem as you, though it was on a larger scale. We couldn't figure it out for the longest. It is a STP problem. It turned out that the problem was created from a blade on one of our 6500’s. The blade just needed to be restarted. We found this by taking down all redundant links. We waited and then started to bring everything up one at a time. We took I believe 15 or so minutes to wait and see if the problem started back up. Once it did we then isolated that switch. I don't know how large your network is, or how much time you have, but this was the fix action for me. I am sure there is a better way that I just don't know it.Good Luck

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