From: Curtis Call (curtiscall@xxxxxxx)
Date: Wed Nov 14 2001 - 12:44:56 GMT-3
BGP just selects one route, you won't see two BGP routes to the same
destination in your routing table. (At least you shouldn't)
"Jobson, Eddie" <EJobson@thrupoint.net> wrote:
> 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.
----------
curtiscall@usa.net
OSPF/BGP Practice Exams
www.boson.com\tests\Advanced.htm
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