BGP Loc Pref

From: Williams, Glenn (WILLIAMSG@xxxxxxxxxxxxx)
Date: Fri Nov 30 2001 - 17:06:26 GMT-3

• Next message: ying-chuan.c.chang@xxxxxxxxxxx: "RE: PPP callback with one-way authentication"
• Previous message: Basel Tashkandi: "Re: AGAIN! IGRP OSPF redis"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]

   
Hi,

Just trying to get something right in my mind on BGP.

Let me know if this is correct.

Here is the set up

r3 r4
 | AS1 |
 | |
.|..........|
 | |
R2----------R1
     AS2

R1 and R2 in same AS2 and BGP peers.

R2 loc pref=200 R1 loc pref = 100.

R2 has next hop self for AS2.

R3 and R4 in AS1 of provider.

R1 and R2 receive same route.

OSPF running between R2 and R1 and rest of routers in AS2.

Now...

So let's say due to connections and routing process packet gets to R1 and
final destination is somewhere in AS1.

R1 and R2 receive same info about destination. Both have same weight and
same AS paths.

This is where I get confused......:(

R1 has route to destination in AS1 via BGP Admin dist 20

But R1 says next hop should be R2 because BGP loc pref of R2 is greater.

But OSPF also has route to R2

So route to R2 is via OSPF because OSPF admin is 110 and IBGP is 200.

So route table in R2 says route to destination is AS1 is via OSPF.

R1 receives packet and sends to R3 since it's Loc Pref is lowest.

R1 never shows a route in BGP table to same destination via R2 (not sure
why)

Does this all sound correct?

GW

• Next message: ying-chuan.c.chang@xxxxxxxxxxx: "RE: PPP callback with one-way authentication"
• Previous message: Basel Tashkandi: "Re: AGAIN! IGRP OSPF redis"
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] [ attachment ]

This archive was generated by hypermail 2.1.4 : Fri Jun 21 2002 - 06:45:27 GMT-3