[c-nsp] Best Practices for quickly removing routes when BGP peer drops

[Gert Doering]

Hi,

On Wed, Dec 10, 2025 at 05:49:47PM +0000, Jakob Heitz (jheitz) via cisco-nsp wrote:
> advertise best-external without labels causes transient forwarding loops. In BGP those could last 10s of seconds. You could use labels or add-path.
> (add-path could cause loops too. C???est la vie)

True, using labels is the best choice to avoid this sort of transient
loops.

The problem with IOS XR is not that "without labels you would see transient
loops", the problem is that it's not working correctly *at all* (because XR
- at least the versions we discussed with TAC for - installs both "best"
and "best external" path as load-sharing entries, and so half your packets
are sent the wrong way).

gert
-- 
"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             gert at greenie.muc.de
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