Sharing routes between carriers using BGP

Question:

I currently have 14 US offices WS-C3560X-24P-L connected via MPLS.  We have recently opened a new office in Ottawa Canada.  Our primary US MPLS carrier cannot provide services in Canada.  I currently have a site to site tunnel setup between Ottawa (Internet circuit) and our head quarters in the US.  It works, but at times we experience connection issues.

I am in the process of ordering MPLS services from a different carrier.  Below is what I have in mind of doing.

                               ------------------ Chicago Head Quarters ( Cisco 2951) Primary BGP -------------- MPLS ------------|------------ BGP Remote Office

Core 6509 (Chicago)  |                                                                                                               |                  |

                               |                                                                                                                |-----------------|------------ BGP Remote Office

                                |                                                                                                       

                               -------------------- Chicago Head Quarters ( Cisco 2851) New Carrier----------------MPLS--------|----Ottawa Office

So I would like my Ottawa office to also be able to see my other remote offices.

What would I need to configure on both of my Cisco routers in Chicago and my core 6509 switch?

Answer:

Yes, you should be good to go,

The ASA will participate in the OSPF cluster and it will learn the default route via the Chicago Head-quarters router,

So most of the job will be done on the Core router (where redistribution will happen)

On the Chicago Head-quarters router you will just build the OSPF relationship with the ASA and advertise the default route,

The ASA and internet breakout is in Ottawa, not Chicago.

Jaime - I don't see any problems with what you propose but you will need to alter the design I suggested slightly. You will need to:

1. Configure users in Ottawa to use the MPLS router as their default gateway (not the ASA)

2. Add a default route on the Ottawa MPLS router pointing at your ASA firewall. Do not redistribute this default route into BGP.

3. In Chicago you will need to redistribute your other site and Chigaco subnets from OSPF into BGP and advertise them out to Ottawa.

I would use route-maps in the redistribute statements so you tightly control what you are advertising. This is not essential but it is useful to keep on top of what is being advertised where and can stop things breaking in the future if additional links WS-C3560X-24P-S are added.