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Virtual Connect and Spanning Tree Protocol (STP)

chuckk281
Trusted Contributor

Virtual Connect and Spanning Tree Protocol (STP)

Meg had a customer question on STP:

 

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My customer is asking about what VC does with a ‘device’ that is using spanning tree.  I told him VC doesn’t participate, but they want more detail.  Does VC drop the communication or does it just ignore it and pass it along.  The info below from the customer is his exact question…

 

Meg,

 

If the upstream switch is sending STP Bridge Protocol Data Units (BPDUs) for vlan 100 for example, to the Virtual Connect module via the SUS (Shared Uplink Set) and the VC is running in mapped mode, will the VC forward the BPDU for vlan 100 to the server port.

 

We have an situation where an application needs to “see” the STP BPDU’s.

 

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Mark Replied:

 

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It depends on if the upstream switch is running IEEE STP or a Cisco proprietary version of Spanning Tree.

 

  1. VC ports do not participate with any upstream switches using STP period
  2. IEEE BPDUs (01:80:c2) are absorbed by the uplink port  and not forwarded to downlinks
  3. Cisco BPDUs (01:00:0c) are treated like any other multicast frame and would be forwarded on

 

If the application needs to see “IEEE BPDUs”, this is not possible. If “Cisco BPDUs” along as the VLANs match it will be forwarded and Server ports would receive.

 

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Any other comments or suggestions for Meg?