I have a client whose office accesses all resources over the internet (hosted email, vpn, etc) and they have one T1 to the internet which goes down way too often.
If they get an additional T1 from a different ISP can the 1721 handle both? Multilink? Aggregating the bandwidth would be a bonus but the main goal is to have some sort of failover.
Could someone explain me how to accomplish this?
Thanks a lot,
There are a couple ways to do it and each provides a slightly different result. To choose the better option you need to clarify what the customer's requirements really are. In the original post it implies that they are most interested in increased bandwidth. The way to achieve this is to have both T1s active and to have two default routes.
If the customer is really more interested in having a primary path and a failover path then you want both T1s active and a regular static default route and a floating static default route. It sould look something like this:
ip route 0.0.0.0 0.0.0.0 s0
ip route 0.0.0.0 0.0.0.0 s1 250
The 250 on the end of the second default route is an administrative distance and it means that as long as the primary default route is available it is in the routing table and is used. But if there is a failure on s0 then the route is removed from the routing table and then the route using s1 would be inserted into the routing table.