BGP Routing Migration

[Simon Young]

I am migrating from one provider to another

I have my original connection - 3750 to external ISP A

I have 2 * 3925 routers, each having a connection to ISP B

Both routers connect to a 3850 as follows, internal peering on loopbacks, routed interfaces on the switches

I want the 3750 to learn the routes from the 3925s

The 3750 could have next hop self, so the 3850 learns all the routes, how do I get the 3750 to learn the 3925 routes as it passes through an ibgp peer

eventually ISP A will disappear along with the 3750 and the 3850 will be the primary entry point to the network

i could connect the 3750 to the routers but wondered if there was an easy way to do this

[Jon Marshall · Accepted solution]

Simon

You say you want the 3750 to learn the routes from the 3925 routers, do you want the 3750 to use those routes over the ones it learns from ISP A.

Are you redsitributing BGP from the 3925s into OSPF on the 3850. If so the 3750 would learn the routes that way.

But if you specifically want to use IBGP then you need to make the 3850 a route reflector and the 3925s and the 3750 route reflector clients. That way any routes received by the 3850 from either of the 3925s could be passed to the 3750 and vice versa.

Perhaps though you could clarify on the OSPF/BGP interaction and what exactly you want to achieve in terms of route preference for the 3750 ?

Jon