UDLD cause STP loop?

[l-gu]

I want to verify UDLD function of Cisco 4006 and Cisco 6509, first I want to see STP loop caused by uni-birdirectional link problem, and so remove a Rx fiber on blocking port of Cisco 4006, but STP loop problem doesn't happen, and both two ports connect cisco 4006 and cisco 6509 are down.

My network is as follow:

Cisco 6509 ---------------------Cisco 4006

++++++++++Other Switch+++++++++++

The port of Cisco 4006 connect to Cisco 6509 is blocking state.

[milan.kulik · Accepted solution]

Hi,

I think you need something more sophisticated to create uni-birdirectional STP problem. There are some keepalives on fiber ports which detect physical disconnect, I think.

So try to connect your Cisco switches via two parallel links and swap Rx fibers between two GBICs on one switch, e.g.

This might work....

Regards,

Milan

[l-gu]

I did, so STP loop occurs.

Thank very much.