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stp set up of wireless bridge


Recently, I was implementing a project in the dock.The environment roughly like this:

     1.there was a fiber link connected 2 LAN  between the 6509 and the 3750X before we want to add a wireless link (using two 1532E APs) to bridge 2 LAN (to transfer several vlans)


The topology like below:

6509:Root Switch      3750:STP Non-Root Switch

AP(left):Root Bridge       AP(right):Non-Root Bridge

Now,I was wondering if  the 2 APs should be seen as transparent or be seen as 2 switches when the wireless link has been established.


Below are 2 doubts I have now:

   1.when I regard the 2 APs as transparent , why the port  that 3750X connected to the AP(right) has been selected as a  designated port but not a non designated one

   2.when I regard them as 2 switches , why the cost from the 3750X to the 6509  hasn't been cumulatived while the BPDU transfer from the 6509  to the 3750X through the 2 aps


Note:I have configured the command "bridge * protocal ieee" for every bridge group which associated to every vlan on both the 2 APs.

By the way,what is the differance between the command "bridge * protocal ieee" and the command "bridge * protocal vlan-bridge"?

3 Replies 3


Two AP act as transparent devices with respect to STP calculation.

If you have allowed a vlan (X) across both fibre link & the radio bridge, please post the output of 

#show spanning-tree vlan X from both 6509 & 3750 switch to check.

One of the port shoud be block in 3750 switch for that vlan & other port should be Root port. Refer this post for the STP root selection rules.




**** Pls rate all useful responses ****


what is the differance between the command "bridge * protocal ieee" and the command "bridge * protocal vlan-bridge"?


We use the bridge number protocol ieee  global configuration command to enable Spanning Tree Protocol (STP) on the bridge. STP is enabled for all interfaces assigned to the bridge group that you specify in the command.

Protocol vlan-bridge is used for inter-vlan bridging.




Simple Concept is that on "bridge * protocal ieee" its running STP globally and * protocal vlan-bridge" is running globally but on vlan basis (logical networks), in wireless bridges.


Mean blocking for VLAN-X is forwarding for VLAN -Y in "protocal vlan-bridge".



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