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AdamDownie12
Beginner

Blocking Port-channel5 on VLAN0001. Inconsistent local vlan.

Hello,

We saw a really unusual issue today on our L2 network.

We have a small network of about 10 switches. Two 3750 stacked switches in the core and the remaining 8 switches connected via portchannels to the 3750 stack.

Today we created a new vlan (102) on all of the switches. The switch core was configured last. The core 3750 stack is configured as the spanning tree root for all vlans so would have become the root. We are running rapid pvst.

As soon as the vlan was created we recieved the below message in the switch log for a number of vlans;

Blocking Port-channel5 on VLAN0001. Inconsistent local vlan.

Then

 Received BPDU with inconsistent peer vlan id 102 on Port-channel1 VLAN1

Then around 5 seconds later

Unblocking Port-channel5 on VLAN0001. Port consistency restored

During the above time all the port channels off the core switch dropped. I have simulated this on other equipment since and not been able to recreate the issue.

Ios version is;

1 30 WS-C3750X-24 15.0(1)SE C3750E-UNIVERSALK9-M
* 2 30 WS-C3750X-24 15.0(1)SE C3750E-UNIVERSALK9-M

Any ideas what this could be?

Thanks

Adam

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