BGP next-hop

Smith W. Stacy stacy at acm.org
Thu Sep 30 19:56:22 CDT 2010


On Sep 30, 2010, at 3:37 PM, Randy Bush wrote:
> it seems it gets the bgp route for 147.28.0.0/16 and then can not
> resolve the next hop.  it would not recurse to the default exit.
> 
> of course it was solved by
> 
>    ip route 147.28.0.0  255.255.0.0  42.666.77.11
> 
> but i do not really understand in my heart why i needed to do this.

Section 9.1.2.1 of RFC 4271 seems to address this. 

A few points from that section:
 - The BGP NEXT_HOP can not recursively resolve (directly or indirectly) through the BGP route.
 - Only the longest matching route should be considered when resolving the BGP NEXT_HOP.
 - Do not consider feasible routes that would become unresolvable if they were installed.

--Stacy






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