Looking closer at routers behoviour in my lab i still belive that what you see is perfectly normal:
1) In phase 1 both routers suck all routes from AS701 and AS1. 2) In phase 2 they send to each other via iBGP connection all routes received from eBGP peers. 3) In phase 3 scanner (or whatever internal name is) is running over both adj-rib-in and selecting best routes 4) In phase 4 best routes are moved to loc-rib 5) In phase 5 some of eBGP routes which has lost in BGP selection in phase 3 and has been advertised over iBGP in phase 2 needs to be withdrawn --- In case when your left router receives from right router better route via Genuity it will keep it, but it will not advertise it back to right router because it was learned via iBGP and it is not acting as route reflector. This is the reason why you see that right routers is receiving only 700 routes from left router..... Browse through routing table on left router. My guess is that all 103300 rotes there is via AS1. Left router will not advertise routes which are not selected (UUNET) and is not advertising back routes learned from right rouer via iBGP. Am I right, or completly mistaken? Przemek On Tue, 2002-02-05 at 20:18, W. Alan Robertson wrote: > ----- 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"] > | | > | _|___________|_ > 700-> > > 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... > ;) > _________________________________________________________________ > CCIE Security list: http://www.groupstudy.com/list/security.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=34558&t=34558 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
