I gather this will adversely effect all those who want to "load balance
across the internet" ;->
Chuck
""W. Alan Robertson"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> - Original Message -
> From: "Ouellette, Tim"
>
>
> > The 2nd router that only has 700 routes in it's routing
> > table that it learned from it's IBGP still has the other
> > 103k routes in it's adj-rib-in from it's ebgp peer right,
> > they are just sitting dormant? So if the other router
> > somehow lost it's ebgp peer, it'll send withdraws to the
> > ibgp peer and the other guy will take over with 104k
> > routes correct?
>
> Exactly...
>
> > Could you define what you meant buy "if an iBGP peer
> > learns that another iBGP peer already has a better route
> > to a specific prefix, it will issue a withdrawl to that
> > peer for the prefix(es)."
>
> Let me see if I can articulate that a little better...
>
>
> [ eBGP ] [ eBGP ]
> [AS 701] [ AS 1 ]
> | |
> 104k| |104K
> | |
> | |
> [ BGP ] [ BGP ]
> [AS "X"] [AS "X"]
> | |
> |
>
> My router that connects to AS 1 has learned roughly 104k prefixes via
> eBGP...
>
> My router that connects to AS 701 has also learned roughly 104k
> prefixes via eBGP...
>
> Via iBGP, the AS1 connected router tells my other router of the 104k
> prefixes that it has learned...
>
> At the same time, my AS701 connected router is transmitting the 104k
> prefixes it has learned to the AS1 connected router...
>
> Once each of my routers has finished their mutual exchange of routes,
> the AS701 connected router sees that for all but approximately 700
> prefixes, the AS1 connected router has an equally good path, and via
> the iBGP connection, he issues withdraws for 103.3k of the routes that
> he had previously announced to my other router...
>
> At this point, each of the routers has a full table learned via eBGP,
> and 'show ip route' yields about 4 gazillion pages of output...
>
> A 'show ip bgp' also yields a ton of output, but the AS701 connected
> router shows two entries for each prefix (One learned via the external
> peer, and one learned via the internal peer), but the AS1 connected
> router has a single entry per prefix.
>
>
> > If both of those routers are receiving full routes, and
> > without any other configuration, how would the routes
> > learned from one provider be any better than the other?
>
> With no additional configuration, "customer" routes (those that
> originate in a directly connected external AS, or are a single hop
> away, if single homed) would be fewer AS hops away... They would be
> preferred...
>
> > Thanks and great post!
>
> Thank you... > ;)
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=34553&t=34550
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