OSPF / BGP / Multiple Gateways Question

RouterOS General
1

Hello,

I have two upstream bgp peers currently hooked into one router (2 eth interfaces) This router has another ethernet interface to my main MT router with 6 eth interfaces which speak OSPF to each other. Then in the other eth interfaces of this router are individual routed subnets to different places of our network with other OSPF speaking routers.

Right now, the main bgp router hooked to upstreams has a default route originate statement in the Quagga config that I presume tell it to advertise its default route 0.0.0.0 so for any address space not owned by me all the routers on the network know to forward the traffic to there for delivery.

I understand how to add more bgp peers to the same router as the other bgp peers but what I do not know how to do is add another bgp peer in another physical location - say another city 10 miles away. Doing this would greatly increase our redundancy capabilities.

So… Questions:
If I place another router (lets say MT) in the new city and acquire a new bgp upstream peer with 3rd provider and tell that router to advertise its default route via OSPF then do all the OSPF routers on my network know about both 0.0.0.0 default routers on both bgp routers and pick the closest one (via OSPF) and if either bgp router dies then the other one will pick up all the traffic?

If I had the same upstream in two different physical locations would it basically work the same way?

I have a strong desire to further distribute all my eggs so they are not in one basket. Any information anyone may have on achieving this would be welcome. I think I have an understanding about how it all works, I just want reinforcing info. to backup what I believe to be true.

Thanks
Scott

2

Believe this is BGP multi-hop is what you are looking for. Another option though, is to just simply create a tunnel between both of your BGP Routers and just run BGP across that tunnel.

3

Well since I am the one asking for more understanding I can’t say that what you proposed is not correct, but I’ll reply to it with my comments…

I’m not even sure what bgp multihop is, but I’ll look into it. I am thinking really it doesn’t have anything to do with bgp at all - just how the external gateway routers advertise internally with ospf… but… If I knew for sure I wouldn’t be asking. I do appreciate your responses though.

I will certainly not want to make a tunnel between bgp routers, that couldn’t possibly server any useful purpose. The internal network routers need to make a decision on which interface to send a packet a long time before it shows up at a particular bgp router.

Scott

4

Well if you are not sure what bgp multihop is, then it is better to get a good BGP book and read it.