[c-nsp] ebgp load balancing using maxiumu-paths TCAM impact on Sup720-3BXL?

Phil Mayers p.mayers at imperial.ac.uk
Thu May 21 09:11:38 EDT 2009

Peter Kranz wrote:
> Setup is as follows; 2 edge routers, each with a BGP session receiving full
> routes to the same provider router. The provider is load balancing inbound
> traffic to our AS nicely, 50/50 between the edge routers.. I would also like
> to load balance the outbound traffic.. I've considered adding 'maximum-paths
> 2' to install the two equal paths, but an concerned about FIB TCAM impacts.
> Will adding this command cause each equal cost route to take one additional
> TCAM entry, i.e. full routing table x 2 > 524k TCAM limit = EPIC meltdown?

I'm not 100% certain about this, but my understanding is that there is 
still only 1 FIB entry for the route; it just has >1 next hop.

However - will this work? For eBGP-multipath, the paths have to be 
basically identical except next-hop. This won't be the case, since each 
router will prefer its direct link (lower IGP cost).

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