udld and normal mode

[sarahr202]

hi every body!

i have a question about udld normal mode.

Udld normal mode does not disable the port, rather it allows the port to operate and generate syslog message.

That means such mode will not help prevent loop in switched enviroment. Then why should one use udld normal mode ?

thanks a lot!

[Mark Yeates · Accepted solution]

Sarah,

It does not seem that UDLD normal mode would be useful, but it can be. Normal mode is just a more conservative method of UDLD, and is more tolerant to false positives like aggressive mode can. Normal mode will shut down a port only if it can explicitly determine that the associated link is faulty for an extended period of time. Here are a few reasons why Normal mode could be a better choice.

High latency links

Highly congested links

Known meaningful network events

Primarily I've only seen UDLD normal mode used on critical Point to Point links. Check out the RFC as it has a lot of good information.

http://tools.ietf.org/html/rfc5171#section-3

Hope this helps,

Mark