BGP prefix filter list

Karsten Elfenbein karsten.elfenbein at
Fri May 17 15:46:15 UTC 2019

Can you check the actual FIB usage? With 2m IPv4 divided into v4 and v6 *
Fast ReRoute could hit the limit.

Baldur Norddahl <baldur.norddahl at> schrieb am Mi., 15. Mai 2019,

> Hello
> On Wed, May 15, 2019 at 3:56 PM Mike Hammett <nanog at> wrote:
>> What is the most common platform people are using with such limitations?
>> How long ago was it deprecated?
> We are a small network with approx 10k customers and two core routers. The
> routers are advertised as 2 million FIB and 10 million RIB.
> This morning at about 2 AM CET our iBGP session between the two core
> routers started flapping every 5 minutes. This is how long it takes to
> exchange the full table between the routers. The eBGP sessions to our
> transits were stable and never went down.
> The iBGP session is a MPLS multiprotocol BGP session that exhanges IPv4,
> IPv6 and VRF in a single session.
> We are working closely together with another ISP that have the same
> routers. His network went down as well.
> Nothing would help until I culled the majority of the IPv6 routes by
> installing a default IPv6 route together with a filter, that drops every
> IPv6 route received on our transits. After that I could not make any more
> experimentation. Need to have a maintenance window during the night.
> These routers have shared IPv4 and IPv6 memory space. My theory is that
> the combined prefix numbers is causing the problem. But it could also be
> some IPv6 prefix first seen this night, that triggers a bug. Or something
> else.
> Regards,
> Baldur
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