From: Charles Manafa (charles.manafa@xxxxxxxxxxxxxxxx)
Date: Wed Nov 14 2001 - 19:13:25 GMT-3
I think you will find that "maximum-paths" BGP router config, will allow BGP
to use up to 6 equal paths to the destination.
----- Original Message -----
From: "Curtis Call" <curtiscall@usa.net>
To: <ccielab@groupstudy.com>; "Jobson Eddie" <EJobson@thrupoint.net>
Sent: Wednesday, November 14, 2001 3:44 PM
Subject: Re: [MED problem]
> 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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