I would also recommend setting a priority on both sides, either to ensure your traffic is being equally shared between core routers, or B because you want one link preferred downstream (presuming all paths are equal). Higher priority wins in this case, opposite of say spantree priorities on vlans.
Of course, you're right. I didn't mention priority to make it light. I used to
Actually what I want is having the failover take precedence if any of the interfaces of the main router goes down. I wonder wether it is possible to have the same standby group for all interfaces. The problem is that I can't test it as the main router is running and the 2nd is in "manual" standby (i.e. stopped).
Actually that's an excellent hint. I didn't think of it. I have no idea on how to make it. Maybe removing the preempt command on the emain router would be enough but, then I have to be careful when starting the routers. Or maybe I can set the preempt command, just when I want to revert back to the main router.
You're right I didn't tell much I thought it was enough. Currently there is 1 router in charge of intervlan routing It's a 2611xm with sub-interfaces on the only Fast Ethernet Fortunately there are only 2 vlans Unfortunately the admin vlan is the base vlan for the branch. The other router is a 2610 and is supposed to have the same configuration except that it has only an ethernet interface. It is kept off awaiting that the main router fails. My predecessor did it this way, because he didn't know anything about fault tolerance.
I made a configuration similar to the one I want with 3550 L3 long time ago and it worked well because they were in charge of both L2 (with RPVST) and L3 transport
Here, as you can see, I don't monitor a wan interface, but by extrapolation, I think I can consider 1 interface as the wan interface of the other (it'd be the idea)