From: Mingzhou Nie (mnie@yahoo.com)
Date: Wed Oct 02 2002 - 22:06:40 GMT-3
Brian is correct. What you have seen is a very common scenario in BGP.
For ibgp peers, each peer is only going to send the best route(the one
with >) to its ibgp peers. Originally, both routers learns 10 network
thru EBGP and prefer than path, so each select EBGP path as best, thus
adv to its IBGP peer. Now local pref has been increased on right
router, on left router, it no longer preferS EBGP path, rather it
select IBGP path thru right router as best, this it quits adv 10 netw
learned thru EBGP to right router.
HTH,
--- Brian Dennis <brian@5g.net> wrote:
> The left router will send the routes that it selects as best to its
> neighbors. The left router isn't using its EBGP route to AS1 so it's
> not
> going to send it to the right router. This is why the right router
> only
> has one route.
>
> Brian Dennis, CCIE #2210 (R&S/ISP Dial)
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> Svuillaume8@aol.com
> Sent: Wednesday, October 02, 2002 10:23 AM
> To: ccielab@groupstudy.com
> Subject: BGP local pref help
>
> Hi,
>
> If i've two routers with an IBGP session.
> Each router has an Ebgp session to the same AS which announce a
> network
> 10.0.0.0.
>
> -----
> |AS 1 |
> _____
> | |
> ________|________|_____
> |AS 2..............AS2 |
> |______________________|
>
> When i let the default parameter my two router have two
> bgp route in thier bgp table.
> In the right router, one to the left router and an other to AS1,
> however
> the best route is EBGP
>
> *>10.0.0.0 to AS1
> * 10.0.0.0 to AS2 (left router)
>
> the bgp table is symetric in the left router.
>
> Problem is when i change default local pref in the right
> router, then my right router hasn't two route but only
> one, to AS1, but i have two routes in the left router
> one to AS1 and an other to AS2 (ibgp)????
>
> Is it normal or not?????
>
> Is the same symptom with MED????
=====
Mingzhou Nie, CCIE #10342
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