On Tue, Oct 21, 2008 at 4:16 PM, Dan Armstrong <[EMAIL PROTECTED]> wrote: > We have a fairly similar design for our Metro Ethernet network. > > Our primary method of protection is STP(MST). I've been thinking about > this, and I can't come up with a reason why we even really need an IGP down > to the edge PE devices? Since it's all layer2 - the core switch/routers see > all of the PE<>core links as Connected routes anyway - what's the point of > bother pushing your IGP down there? It's just more needless routes. > That leaves you with a very small IGP in your core.
The problem is that you are supposed to have redundant links between routers. The way to have permanent links between routeurs in spite of changing routes and falling interfaces is to establish communication between loopbacks, and that is what LDP and iBGP - MPBGP do. Therefore you need unfettered communication between the loopbacks of your routers, PE routers included, therefore you need your loopbacks in your IGP, therefore you need IGP on your PE routers. I suppose you could somehow make the network function without it, but you'd lose redundancy at the very least. -- Nathan _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/