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New Member

vlan 1 is flapping

Hello I have a problem.

c4006s#sh logg

Syslog logging: enabled (0 messages dropped, 22 messages rate-limited, 0 flushes

, 0 overruns)

Console logging: level debugging, 1031 messages logged

Monitor logging: level debugging, 0 messages logged

Buffer logging: level debugging, 1053 messages logged

Exception Logging: size (8192 bytes)

Trap logging: level informational, 1058 message lines logged

Log Buffer (4096 bytes):

ort Fa6/15 and port Gi1/2

7w2d: %C4K_EBM-4-HOSTFLAPPING: Host 00:12:F0:7E:A8:CF in vlan 1 is flapping betw

een port Fa2/16 and port Gi1/2

7w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:14:BF:03:A7:AD in vlan 1 is flapping betw

een port Gi1/2 and port Fa6/15

7w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:12:F0:7E:A8:CF in vlan 1 is flapping betw

een port Fa2/16 and port Gi1/2

7w3d: %C4K_EBM-4-HOSTFLAPPING: Host 00:12:F0:1D:83:1E in vlan 1 is flapping betw

een port Gi1/2 and port Fa6/15

7w4d: %C4K_EBM-4-HOSTFLAPPING: Host 00:12:F0:7E:A8:CF in vlan 1 is flapping betw

een port Fa2/16 and port Gi1/2

Anyone can help me?

8 REPLIES
Hall of Fame Super Bronze

Re: vlan 1 is flapping

A device connected on port Fa2/16 is reporting the same MAC address as device on G1/2

A device connected on port Fa6/15 is reporting the same MAC address as device on G1/2

Please tell us what devices are connected on G1/2, Fa2/16 and Fa6/15

New Member

Re: vlan 1 is flapping

Hello in G1/2 I have other SW 4006 and both are in mode HSRP protocol,this is trunk.

In Fa 2/16 y fa 6/15 both are PC notebook.

Thanks.

Hall of Fame Super Bronze

Re: vlan 1 is flapping

It sounds like you have a loop. The other switch shouldn't report those MAC addresses. How many links the other switch has to this switch ?

Do you have only 2 switches ?

New Member

Re: vlan 1 is flapping

I have only 2 switches, but exist a Access Point in Network.

Several PC notebook connected to AP throught of card wireless Network .

Re: vlan 1 is flapping

This is normal occurrence with wireless users as they may connect to the network via different APs at different times. Both APs are probably not connecting to the same core switch and that's the reason switch logs this error message.

If you want to stop this you need to configure the laptops to use a particular AP rather than any available AP.

HTH

Sundar

New Member

Re: vlan 1 is flapping

ok , I have a question what problem may occurs if this PC Notebooks appears as Host 00:12:F0:7E:A8:CF in vlan 1 is flapping betw

een port Fa2/16 and port Gi1/2

Can you explain what cause of this condition in my Network.

was this able to affect my network negatively?

Re: vlan 1 is flapping

Let's say you have AP1, AP2, switch1, switch2, wireless userZ. AP1 connects to switch1 and AP2 connects to switch2.Switch1 and switch2 are interconnected.

UserZ connects to switch1 through AP1. Switch2 would know that it can reach userZ via switch1. UserZ disconnects and reconnects to switch2 via AP2. At this point switch2 would say, wait a minute I was seeing userZ connected through a different port earlier and now it's a different port. It generates this log message as a warning that there could be a potential problem out there in the network. This symptom can also occur if there's a spanning tree issue but not in your case though.

HTH

Sundar

New Member

Re: vlan 1 is flapping

Hello, I have a one question, how can I configured a port by way AP with relationship a Spanning Tree , you can to tell me what is configuration correct to the port with AP.

is spanning tree portfast correct?

Thank.

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