Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

MST/PVST Boundary

I have an MST region with istance 1 mapped to vlans 1-500. The MST boundary switch has an interface which connects to another switch running PVST.

My question is, when a BPDU is sent from within the MST instance 1 for VLAN 45 (for example), will the PVST region recieve BPDUs for just VLAN 45 or for all VLANs mapped to the MST instance (1-500)?

I am confused by this line in the 6500 series command reference guide;

"The ports that belong to the MST switch at the boundary simulate PVST+ and send PVST+ BPDUs for all the VLANs."

Any help would be much appreciated!

Thanks,

Tom.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: MST/PVST Boundary

Hi Tom,

The Cisco MST switch detects neighbor running PVST as soon as it received a PVST BPDU. Then, it replicates the BPDU for instance 0 (the CIST) on each an every vlan configured on the port. This is a boundary port, meaning that only the CIST information is relevant (your MST instance 1 information will not be used). So on the PVST switch, each vlan receives a BPDU coming from the MST bridge, and each vlan instance receives information from MST instance 0.

HTH,

Francois

3 REPLIES
New Member

Re: MST/PVST Boundary

An mst region appears to the rest of the network as ONE bridge, so the switch that connects mst to pvst will send a bpdu representing the entire region.

New Member

Re: MST/PVST Boundary

It is better for you to Switch only to PVST+

because if there is a loop on MST Region it will block all VLAN's for PVST+.

Re: MST/PVST Boundary

Hi Tom,

The Cisco MST switch detects neighbor running PVST as soon as it received a PVST BPDU. Then, it replicates the BPDU for instance 0 (the CIST) on each an every vlan configured on the port. This is a boundary port, meaning that only the CIST information is relevant (your MST instance 1 information will not be used). So on the PVST switch, each vlan receives a BPDU coming from the MST bridge, and each vlan instance receives information from MST instance 0.

HTH,

Francois

1123
Views
0
Helpful
3
Replies
CreatePlease to create content