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
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.
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
i don't know exactly why you want to to this but you should do like this :
RA <=EBGP=> ISP
RB <=EBGP=> ISP
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'