P2P link load balancing help require

[Dhiraj Jagdale]

We have two p2p links in between two branches connected to two different routers at both ends, we want to load balance traffic on this two links from both ends. 

Please help. Thanks in advance.

[Joseph W. Doherty]

If your running an IGP that supports ECMP, by default, most Cisco routers will load balance across 4 paths.

Often, though, if your branch routers are also the gateway routers, traffic starts on one router, and will not use the other router, because once your traffic is on the one router, it's no longer ECMP unless you "tweak" your IGP's metric settings.

If two routers, you can sometimes use something like GLBP or mHSRP to get traffic split before it gets to your routers, so ECMP operates.

EIGRP can optionally support unequal cost load balancing.

If your routers support PfR, it too can support load balancing.  Unlike IGP load balancing, PfR can do dynamic load balancing and/or support ECMP or unequal cost multiple path.

[Richard Burts]

Joseph has some good comments about the challenges of using Equal Cost load balancing with the dynamic routing protocols when there are two routers on each end. I like the concept of having two HSRP groups at each site. One HSRP group has router A as the active router while the other HSRP group has router B as the active router. With some hosts in the first HSRP group and other hosts in the second HSRP group you will achieve load balance for outbound traffic, and will also have failover in the case that one router goes out of service.

We do not know much about the topology but if there were two subnets at each site it should be possible to set up routing so that one subnet was reached by one P2P and the other subnet was reached by the other P2P. This would work with static routes and EIGRP but might be a bit of a challenge with OSPF.

HTH

Rick