Why can't 2 ethernet ports communicate if both are using spanning tree?

[iscoro]

I have a 3com switch and a wireless bridge (350 series) both connected via ethernet ports ( Both the switch and the bridge ara using spanning tree). It happens that they can't communicate with each other after a random period of time, the wireless bridge link is up, but no data passes through the port. To solve this, I have to disconnect and reconnect the ethernet cable of the bridge's ethernet port.

Anyone has an idea why is this happening?. I suspect it's a spanning tree problem, but I'm not sure if that is the problem or why.

[Tsasbrink]

If so you can check who of the two is the root and to change the root you must lower the priority of the non root bridge to for example 8192, if this solves the problem it indead is a spanning tree problem with te formerly root bridge. But if you can be shure no loops can exist why are you using spanning tree in the first place ?

[rjackson]

Sounds like the 350 is plugged into the 3com switch. What's plugged into the other 350? Does the problem clear when you unplug either end or just the one where the 3com is? Spanning tree should not be an issue unless there is a loop in the network. More likely the 3com is getting errors and shutting down the port where the 350 is connected. Could be a speed or duplex mismatch. Try forcing both devices to the same hard set speed and duplex.

[iscoro]

At fisrt we thought of that (the duplex mismatch), but It didn't solved the problem, we forced them to full duplex and It keeps happening the same thing. answering to your questions, the other 350 has another 3com switch (even the same model: 4005). At first we thought of a layer 2 compatibility problem, but we have no exact clues to that. The problem solves (for a while) if we unplug the 350 end of the ethernet cable. Answering your comment about the errors on the 3com switch, We checked already the system log for errors, but everything seems normal.

Any comments?