Overriding Default routes with BGP
I have a customer with 2 carriers. They have their own ASN, and are running BGP to the carriers. Unfortunately, they are using HSRP on their carrier facing routers. Without explaining all of that and the problems they run into, I thought okay simple solution we will run iBGP from their border routers back to the WG. I have that all set up with no problems.
However, no matter what I try I cannot override the built in default routes in the WG. If I disable Multi-Wan it forces me to enter a default route. I do not want a statically defined default route. I want BGP to do its thing.
If there is a default route learned from the carriers I want to pass that on from the border routers to the WG. I have multi-path (BGP config) set up in BGP. If both routes to the carriers are up, those default routes should flow down to the WG and the routing table should do its thing. This all works great. I see the learned default routes in BGP and the RIB. However, if an upstream link goes down and my WG facing router no longer advertises a default route to the WG, the WG still leaves a default route in place, obvious bad things to happen.
I've spent many hours trying everything I can think of. Custom interfaces, setting the default route to different things. Anything to try to over-ride the default route so iBGP and the RIB can take over. No matter what I do, both external interfaces have a route in the RIB, even though they shouldn't. The problem is if the outage is upstream the WG will still send traffic out that direction.
The best solution I've come up is setting up multi-wan with link monitor. I really did not want to do that. Dynamic routing protocols were invented to handle these situations.
So, my question is how can I set up a WG to prevent an external (whether it is set to that or not) interface from putting a default route into the RIB?