Hi Adam,
Thanks for the reply. I'm still in doubt though.
If we look here for example:
https://xrdocs.io/ncs5500/tutorials/ncs5500-fib-programming-speed/
we see that BGP programming speed is always faster than FIB programming
speed.
If best path is advertised regardless of the FIB state by default, this
would always mean a potential for longer/shorter blackhole...
Thanks,
Marcin
W dniu 26.02.2020 o 14:13, [email protected] pisze:
Hi Marcin,
There was a thread on the topic of slow FIB download/upload on this forum
some time back.
Yes BGP will advertise the best path regardless of the FIB state by default.
I'd recommend enabling it. (though subject to testing on your code version
as always)
adam
-----Original Message-----
From: cisco-nsp <[email protected]> On Behalf Of Marcin
Kurek
Sent: Friday, February 21, 2020 10:40 AM
To: [email protected]
Subject: [c-nsp] bgp update wait-install - RIB/FIB inconsistency
Hi all,
During a recent MW I ran into a fishy situation.
Long story short - ASR9001 running XR 6.4.2 SP4 was rebooted, after it
went
back online I noticed slow route installation in FIB. It took around 20
minutes
to install > 700k prefixes.
Apparently, some customers experienced problems at that time, so I'm
suspecting some RIB/FIB inconsistency here.
I've been researching this topic for a while and now I'm even more
confused.
Can someone help me answer below questions, please?
Assuming our router has established its e/iBGP sessions and finished
receiving updates from its neighbors, will it advertise its best paths
even
though FIB programming is still in progress?
Common sense answer would be "no", because if it starts advertising
prefixes that are not installed in FIB, it also starts attracting and
possibly
blackholing traffic.
But I discovered the command "update wait-install" as part of BGP RIB
feedback mechanism introduced in XR 4.3. When it's enabled, routes that
have not been installed in FIB are not advertised. Looks like that it's
turned
off by default though.
If so, the answer to my 1st question should be "yes", although to me, it
doesn't make much sense.
I've been trying to find best practices / recommendations for that
command,
but without luck.
Can anyone shed some light on that, please?
Thanks,
marcin
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