How Cisco pvst+ communicate with H3C MSTP?

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Sep 12th, 2010
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Cisco switches are now running PVST+,and H3C running MSTP, how can they talk to each other, without changing any configuration on Cisco site. I know that vlan 1 can prevent loop because the BPDU of VLAN1 is standard.But I don't know other vlans(for example vlan 2,3) if can communicate with each other and prevent loop?  Cisco will consider H3C as hub,and H3C just forward the pvst+ BPDU to another cisco switch but not to deal with it?

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Peter Paluch Sun, 09/12/2010 - 14:03
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Hello Shi,

The H3C should foward the PVST+ BPDUs as multicasts and it should not block or try to interpret them (although this has to be confirmed experimentally as there is no official regulation on this). You were quite on spot with your comment that the H3C will essentially behave like a hub to the PVST+ BPDUs. The Cisco switch will simply react accordingly.

The MSTP running on the H3C emits CST (Common Spanning Tree) BPDUs on its boundary ports and thus will interact with the VLAN 1 BPDUs sent by the Cisco switch in usual manner. If the MSTP decides to block a port towards the Cisco switch then this port on the H3C will be blocked for all VLANs in the MSTP region. There is no per-VLAN semantics on an MSTP boundary port.

Best regards,



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