Testing UDLD on copper interfaces

aandreotti · ‎10-27-2009

Hi all,

I have to verify the correct working of UDLD protocol on copper interfaces.

In my lab two 6509 Catalysts are connected betweeen them with 4x10/100/1000 links, taken form a WS-X6148A-GE-TX port adapter. An Etherchannel is used to combine these links into one logical channel. Autonegotiation is already enabled on the involved interfaces and Rapid Spanning Tree is configured.

I'm planning to enable aggressive UDLD on all these interfaces with the "udld port aggressive" command; I'm looking a way to test if it works. I think the most critical point would be how to simulate an unidirectional link.

Any idea how to implement it? I''ve read on a forum about one possible strategy: to put a non-Cisco L2 device between the two Catalysts and unplug one side after the UDLD peers have been created.

Has anyone tested it successfully? Any other suggestion about alternative ways to have an unidirectional link on copper interfaces?

Thanks

Alessandro

Edison Ortiz · ‎10-27-2009

If you can get 2 additional devices, you can emulate a pseudowire between these two 6500s and break one link while keeping the other link up hence UDLD unidirectional failure.

If you have 2 additional switches, you can configure 802.1q tunnel.

If you have 2 additional routers, you can configure L2TPv3

As matter of fact, I was doing a lab for a customer yesterday with UDLD over Copper running ATOM. It worked quite well on UDLD detection..

Regards

Edison.

Leo Laohoo · ‎10-27-2009

Hi Edison,

Do you recommend UDLD on copper ports?

I had the impression that UDLD would be best suitable for fibre optic ports.

Edison Ortiz · ‎10-27-2009

I've seen cases where a copper LAN port gets stuck - remaining up/up state while the neighbor is down/down. UDLD will detect this failure on the stuck port and errdisable it..

Regards

Edison.

Leo Laohoo · ‎10-28-2009

Thanks Edison. +5

aandreotti · ‎10-28-2009

Hi Edison,

thank you for the reply.

I have only one doubt (consider the case of two additional switches between the 6500s).

Do I have to enable also Layer 2 Protocol Tunneling on the additional switches in addition to 802.1Q Tunneling? I was wondering if I have to do it because on the 6500s RSTP and VTP are globally enabled, an Etherchannel is configured on the back-to-back links and now I have to configure UDLD too...

Thank you, regards

Alessandro

Edison Ortiz · ‎10-28-2009

Correct, in addition to dot1q tunneling - you need to enable l2protocol tunneling for CDP, VTP and STP

http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_l1.html#wp1011486

Regards

Edison

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