bgp conditional peering

[illusion_rox]

hi everyone, i had a question regarding bgp.

Suppose i have 2 routers peering with an ISP ( whether same ISP or 2 different ISP ) lets name these routers RA and RB. i want RB to make a peering session with its ISP if and only if RA fails its bgp session, now u can also assume that RA fails completely or just loses its bgp connection, in either case i want RB to start its own bgp session, so i want to make RB backup of RA in terms of BGP.

how can it be possible

[criss_noh]

yes. that is commonly used. you can have backup line via BGP or have 2 paths likely loadbalancing.

[illusion_rox]

can u kindly tell me that how its possible ? what configuration i have to do ???

[royalblues]

The only way i could think of achieving this is by configuring BGP over loopbacks and making sure that it is reachable only when your primary links come up.

Narayan

[criss_noh]

that is very simple. you just command maximum-path 2. but please make sure all of BGP best path selection procedure.

router bgp 10

neighbor x.x.x.x remote-as xxxx

maximum-paths 2

end

[etienne.basset]

hello

i don't know exactly why you want to to this but you should do like this :

RA <=EBGP=> ISP

RB <=EBGP=> ISP

AND

RA <=IBGP=> RB

then RA set localpref150 on incoming routes,

RB do as path prepend on outgoing routes...

it's more clean than 'conditionnal peering'

Etienne

[criss_noh]

Dear etienne,

I guess that he wants to have 2 paths on the same router. this means link redundency vis bgp not router redundency.