From: Gregg Malcolm (greggm@xxxxxxxxxxxxx)
Date: Sat Apr 13 2002 - 15:41:47 GMT-3
Bradford,
Bradford,
As I understand it, the last 3 decisions that BGP makes to determine the
best route if multiple routes exist to the same destination is as follows
(in order) :
Prefer the route with the nearest IGP neighbor (you might want to do traces
since you are using EBGP Multi)
Prefer the oldest route (I believe that if you clear a neighbor, the router
with multiple routes will switch to the other route and continue to use it
even if the router prefers the route from the router that was cleared (Hope
that makes sense, I confuse myself)
Prefer the route with the lowest router-ID.
HTH, Gregg
----- Original Message -----
From: "Hung, Sing-Yu" <Sing-Yu.Hung@pccw.com>
To: <ccielab@groupstudy.com>
Sent: Friday, April 12, 2002 11:56 PM
Subject: bgp router id?
> Hi,
>
> Does bgp will prefer the path with the lowest router ID? Why
> 172.16.4.0 route will prefer 10.10.10.6 with have a higher router ID?
>
>
> r7#bgp 172.16.4.0
> BGP routing table entry for 172.16.4.0/24, version 5
> Paths: (2 available, best #2)
> Advertised to non peer-group peers:
> 10.10.10.8
> 600
> 10.10.10.5 (metric 20) from 10.10.10.5 (10.10.10.5)
> Origin IGP, localpref 100, valid, external, ref 2
> 600
> 10.10.10.6 (metric 20) from 10.10.10.6 (10.10.10.6)
> Origin IGP, localpref 100, valid, external, best, ref 2
>
> r5#bgp
> BGP table version is 10, local router ID is 10.10.10.5
> Status codes: s suppressed, d damped, h history, * valid, > best, i -
> internal
> Origin codes: i - IGP, e - EGP, ? - incomplete
> * 172.16.4.0/24 10.10.10.5 0 600 i
> *> 10.10.10.6 0 600 i
>
> r7#
> router bgp 500
> neighbor 10.10.10.5 remote-as 600
> neighbor 10.10.10.5 ebgp-multihop 255
> neighbor 10.10.10.5 update-source Loopback0
> neighbor 10.10.10.6 remote-as 600
> neighbor 10.10.10.6 ebgp-multihop 255
> neighbor 10.10.10.6 update-source Loopback0
>
>
>
>
> Bradford Hung
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