Re: [Idr] draft-asati-idr-bgp-bestpath-selection-criteria as IDR WG draft

[Mike Benjamin <mikeb at gblx.net>]

On Thu, Jul 23, 2009 at 12:22:42AM -0400, Curtis Villamizar wrote:
: 
: The first rule just seems obvious and out of scope for RFC4271.  Is
: the first rule saying much more than "If there is more than one IGP
: instance, pick the right one"?  If so is that too obvious to need to
: be stated?


The first rule is stating that if the nexthop lookup resolves to a
path that has no knowledge of the route, it should not be considered.

For example, two LERs that do not exchange their BGP table with the
LSR.  In the event of an LSP failure, BGP still resolves the nexthop,
via an IGP path, installs the route, and the device blackholes
anything destined for it.

The mechanism is stating that BGP should be given the knowledge of
where to look for a valid nexthop.  IGP sourced RIB entries can be
considered to establish the BGP session, but should not be used to
resolve the nexthop if that path has no knowledge of how to get there.

--mikeb

: 
: Curtis
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