Multilink is a way of bundling more than one PPP WAN links and bundle them together into one logical interface. This is one of the method you can implement when you have a primary and secondary links in place and create a logical conduit where both links are present.
This method can be used to load balance data across the links and at the same time it will support redundancy when one one link fails.
I have tested this configuration on 2 of my 2500 Routers and I haven’t tested these on more recent IOS so some commands may vary. I will be checking them on a pair of 3845s/2691s on a later date and will add my findings to this post.
As you can see the Diagram, I am using R4 and R5 which are connected via Serial 0 and Serial 1 respectivly.
Multilink Interface interface Multilink1 ip address 172.16.1.1 255.255.255.252 ppp multilink ppp multilink links maximum 2 ppp multilink links minimum 1 ppp multilink group 1
interface Serial0 no ip address encapsulation ppp clock rate 64000 ppp multilink ppp multilink group 1
interface Serial1 no ip address encapsulation ppp clock rate 64000 ppp multilink ppp multilink group 1
As you can see, since this is a lab scenario, I have set the clock rate on the link. If you are setting this up on a WAN link, you don’t need to do this as the circuit provider would be setting this up for you.Read more