We are building a new border infrastructure and at our borders edge we will have two routers, the next network device will be a pair of Catalyst 4500X switches that will be configure with VSS (see attached diagram). Between the two border routers and the Catalyst 4500X VSS pair will be two equal cost etherchannel groups one going to each border routers for redundancy. My question is, how do the Catalyst 4500X VSS pair determine which interface or etherchannel group to forward packets to the border routers? I would like to have them load balance equally as possible between the two border routers, but didn't know if there was some configuration that needed to be applied to the etherchannel configuration or if it did on it's own. Any information or reference information would be greatly appreciated.
Thanks!
