UDLD Port Configuration

Unanswered Question
Jul 26th, 2007

Hello All,

What is the best practice for UDLD? My network has the standard setup with Core, distribution and access layer switches connected with Gig-E copper cable. The connections between all the switches are trunk-ed. When I issue ?show diagnostic sanity? it recommend I enable UDLD in all the trunk ports. Is it advisable to enable UDLD for all the trunk ports, since the physical connection is copper? Do I gain anything; I always thought UDLD is more helpful using fiber. Thank you in advance for your help.

I have this problem too.
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sundar.palaniappan Thu, 07/26/2007 - 11:12

It's recommended on copper ports as well. Here's an excerpt from the Cisco Catalyst best practices document.

The UDLD feature is intended to address these fault conditions on fiber and copper Ethernet interfaces:

* Monitor physical cabling configurations and shutdown any miswired ports as errdisable.

* Protect against uni-directional links. When a uni-directional link is detected, due to media or port/interface malfunction, the affected port is shut down as errdisable, and a corresponding syslog message generated.

* Furthermore, UDLD aggressive mode checks that a link that was previously deemed bidirectional does not lose connectivity during congestion and become unusable. UDLD performs ongoing connectivity tests across the link. The primary purpose of UDLD aggressive mode is to avoid the black holing of traffic in certain failed conditions.




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