common STP (802.1D) and RSTP (802.1w) compatibility

Unanswered Question
Nov 27th, 2007

I understand that there is downward compatibilty of 802.1w to support lagacy spanning-tree 802.1D. But I need to verify whether the following setup is valid. I have a 6500 as the RB running RSTP which is linked via a trunk (802.1Q) connection to a C3750 switch, also running RSTP, then from the 3750 I have another trunk (802.1Q)link connected to C3550, this switch is running ieee spanning tree, is the uplink switch (3750) able to deteremin it is a legacy BPDU coming from the 3550 on a trunk link? (both have vlan1 as the native vlan) How will the other non native vlans react on the uplink C3750? Should the vlans be on separate interfaces on the 3750-3550 links for the C3750 to deteremin that each VLAN are connected to legacy ieee spanning tree.

I have this problem too.
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ebreniz Tue, 12/04/2007 - 10:54

The two types of STP protocols are compatible. 802.1w should revert to work with 802.1d bridges.

Switches based on IEEE 802.1d specifications can interoperate successfully with RSTP, IEEE 802.1w, since RSTP retains compatibility with older version of STP. Rapid STP is backwardly compatible with 802.1D and transparent to end users. You can have both protocols enabled on the network.

See this url for documentation on this.

bvsnarayana03 Tue, 12/04/2007 - 20:06

As mentioned in other post, RSTP has backward compatibility with CSTP. So your design doesnt seem to bring any issues.


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