BGP Question

[patrick.hurley]

I have customer's network that is running BGP between all the routers. He has two 0/0 destinations, both at different locations. Can I install two routes in the BGP table in the backbone so that one 0/0 is preferred and if it is unreacheable the other 0/0 will be used?

[Giuseppe Larosa]

Hello Patrick,

the answer is yes both border routers can advertise their own 0.0.0.0/0 in iBGP and one can be preferred by using an higher local preference.

Be aware that the backup route can need to be propagated in the domain because routers will advertise only the best path.

So the recovery time when the the primary default fails is given by the propagation time from the second border router to the Route Reflectors to the all the other routers and the bgp scan time on each router to install the backup route.

Another possibility is to leave the two advertisements with the same attributes: in this case for recursion each router will choice the path to the nearest (as per IGP metric) border router, again in case of failure the other path will propagate and will be installed.

lowest IGP metric to BGP next hop

Hope to help

Giuseppe