How to connect redundant routers into an ASA

[campbech1]

I'm attempting to bring two networks together that requires the existing ASA to stay in place for the time being. I have two circuits from our facility to the new facility using different vendors and need to bring them into the ASA for redundancy and circuit bandwidth. I need both of the routed links to be on the same interface back to our facility.

The links from each of the bmh-4451-1 and bmh-4451-2 are using different circuit vendors. What's the best way to use redundant routers into the ASA while using both links?

Attached is the diagram I'm working with.

Thanks in advance for any assistance.

[Walter Astori]

In your environment, do you use a dynamic routing protocol as OSPF ? If you use OSPF you can enable load balancing between two link with OSPF

[Richard Burts]

The drawing provided by the original poster shows the two routers and the ASA with each router connected to an ASA interface which suggests that each of the router to ASA links is a separate routed subnet. In that case the ASA can have a default route using one interface (and perhaps a backup default route using the other interface). But the ASA will not load share the default route over both interfaces.

I have a customer with a somewhat similar situation. They use one link as their primary Internet connection and use the second link for separate traffic such as site to site VPN traffic. They have some traffic on each of the outbound connections and they do have failover capability. But they do not really have load sharing from the ASA which I think is what the original poster wants to accomplish.

I have another customer with a somewhat similar situation. But this customer put a switch between the ASA and the routers. This uses one ASA interface and makes the connection to both routers into a common subnet. They had implemented HSRP on the router interfaces to improve failover if an upstream link had a problem. I did a project for them that replaced HSRP with a dynamic routing protocol (in this case it was EIGRP but any dynamic routing protocol should do). This allows the ASA to actively send some traffic to the first router and to send other traffic to the second router and improves the load sharing of the routers. Note that the ASA can forward traffic to two different next hop addresses only if they are both reached through the same outbound interface. Perhaps the original poster might implement something like this.

HTH

Rick