[c-nsp] UDLD - why is default 60 seconds?

Saku Ytti saku+cisco-nsp at ytti.fi
Thu Feb 23 12:06:33 EST 2006

On (2006-02-23 18:32 +0200), Hank Nussbacher wrote:

> <http://www.cisco.com/en/US/products/hw/routers/ps368/products_configuration_guide_chapter09186a0080160ecf.html>
> Why is the default probe message time 60 seconds and in addition one can
> only go as low as 7 seconds?  If a GE port suddenly becomes
> unidirectional, I would like to know about in 1-2 seconds and not after 7
> seconds, so that the link is forced down and OSPF turns to an alternate
> path.  Or am I missing something?

 Valid question, which I don't have answer to, I agree they're quite
conservative. But I'd suggest that you'll solve your rapid IGP
livelyness detection with BFD instead, UDLD only helps in very spesific
problem, which should happen extremely rarely.

 Also you may want to complement UDLD with STP loopguard, to cover
another corner case (mainly STP software issues).

> Thanks,
> Hank
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