BGP peering strategies for smaller routers

lincoln dale ltd at interlink.com.au
Mon May 2 20:27:40 UTC 2016


>
> You have to keep in mind there are two pools of memory on the router.


There's actually three.

1. Prefix (path) via BGP:  "show ip bgp <prefix>".  BGP will select the
'best' BGP path (can be multiple if ECMP) and send that through to the RIB.
2. RIB. "show ip route <prefix>".  routing table will show the path chosen
- and if there are backup paths etc, but may be recursive, e.g. prefix
a.b.c.d points at e.f.g.h which in turn points at i.j.k.l etc.
3. FIB. basically fully resolved prefixes.

What you otherwise say is correct - you could have N transit providers at
(1) providing lotsOfPaths x N providers which ultimately resolve to
lotsOfRoutes with up to N next-hops.
Much design effort goes into the routing stack to efficiently store
lotsOfPaths.

Can't speak for what an ASR1K does but suggest the OP talk to Cisco.


cheers,

lincoln.


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