From: Jobson, Eddie (EJobson@xxxxxxxxxxxxx)
Date: Wed Nov 14 2001 - 08:06:09 GMT-3
I am having problems getting both routes to an external BGP neighbor when
setting different metrics. Can anyone tell me what I'm missing. The only
thing I haven't tried yet is the deterministic commands.
Diagram
------------
| Ext. |
| BGP peer |
-------------
| |
| |
| |
--------- ---------
| Rtr A | | Rtr B |
TKR1---------| | | |-------TKR2
---------- ----------
| |
WAN 0 | | WAN 1
| |
--------
| Rtr C |
| RR |
---------
The EBGPpeer is peering with both Rtr A & Rtr B but want it to prefer TKR1
on RtrA and TKR2 on RtrB, unless either of the links fail. If so and the Rtr
B to EBGP peer fails use the Router reflector RtrC to get to TKR2 and vice
versa.
I've tried various enabling of next hop self, redistribute connected,
network staements all in different combinations but no luck. I get TKR1
showing up as a metric of 50 when all links are up and TKR2 as a metric of
50, but I would have expected a less preferred route with a metric of 60
also shown without the > sign in the show ip bgp table. If I pull one of the
links I loose the route, but I have full connectivity between RtrA-RR-RtrB
over IBGP/IGP.
Configs
RtrA
router bgp 1
neighbor EBGPpeer remote-as 100
neighbor EBGPpeer upd lo0
neighbor EBGPpeer route-map med out
neighbor EBGPpeer ebgp-multihop 5 (there is another router in the way not
shown on the diag)
network TKR1 mask 255.255.255.0
network TKR2 mask 255.255.255.252
neighbor RtrC remote-as 1
neighbor RtrC upd lo0
neighbor RtrC next-hop-self
no sync
route-map med permit 10
match ip add 1
set metric 50
route-map med permit 20
match ip add 2
set metric 60
route-map med permit 30
access-list 1 permit TKR1
access-list 2 permit TKR2
RtrB
router bgp 1
neighbor EBGPpeer remote-as 100
neighbor EBGPpeer upd lo0
neighbor EBGPpeer route-map med out
network TKR1 mask 255.255.255.0
network TKR2 mask 255.255.255.252
neighbor RtrC remote-as 1
neighbor RtrC upd lo0
neighbor RtrC next-hop-self
no sync
route-map med permit 10
match ip add 1
set metric 50
route-map med permit 20
match ip add 2
set metric 60
route-map med permit 30
access-list 1 permit TKR2
access-list 2 permit TKR1
RtrC
router bgp 1
neighbor RtrA remote-as 1
neighbor RtrA upd lo0
neighbor RtrA route-reflector-client
neighbor RtrB remote-as 1
neighbor RtrB upd lo0
neighbor RtrB route-reflector-client
no sync
EBGPpeer
router bgp 100
neighbor RtrA remote-as 1
neighbor RtrA ebgp-multihop 5 (hidden router)
neighbor RtrB remote-as 1
That's it! As I say full IP connectivity and routes being received when all
links are up, but less preffered metric 60 routes do not appear?
Any help appreciated,
Eddie.
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