Tag Archives: Routing

Avoid Cisco FIB/TCAM exhaustion on full BGP table feed

The number of IPv4 prefixes in the global BGP table is approaching the limit of many Cisco products, such as 7600/6500 RSP720/Sup720 and some ASR1000, which may hold a maximum of ~500K routes in their FIB (the Forwarding Information Base, where only best paths are stored).

These routers can usually handle a bigger load of prefixes, they can also be used to receive the full BGP table from many upstream providers concurrently, but they can’t manage more than 500/512K entries in their RIB or FIB.

Routing protocols to FIB

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One single route-map for both IPv4 and IPv6 BGP prefixes

I just want to share here a note-to-myself about route-maps and IPv4/IPv6 BGP prefixes matching.

R1 and R2 were BGP speakers, R1 was announcing both IPv4 and IPv6 prefixes to R2 and I wanted to set, let’s say, different weights on those prefixes: weight = 4 to the IPv4 prefix and weight = 6 to the IPv6 prefix. It’s stupid, of course, but it’s just to simplify the real task I had to face. 🙂

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