On Fri, Aug 31, 2012 at 9:21 AM, <Bill.Ingrum@t-systems.com> wrote:
I think having a GRE tunnel for the internal routing protocol is unnecessary. Can you explain the reasoning behind this? I understand the technical issue whereby GRE will allow multicast for EIGRP, OSPF, etc, but why not just redistribute into BGP?
I work on a lot of MPLS CE routers, and in general you can accomplish anything you need by redistributing your internal routing protocol into BGP, and adjusting LP, MED and AS Prepend as needed.
Thanks, Bill
So, rather than run an IGP between siteA and siteZ across a GRE tunnel, you'd prefer to redistribute your IGP into BGP at siteA, advertise those routes upstream...and at siteZ, accept the routes in via BGP, and then redistribute them into the IGP for the other routers at siteZ, and vice versa? Or would you have every router at siteA and siteZ participate in BGP, so that all the routers at siteZ get the routes from siteA intact? (choice B tends to have practical implications on what network gear you can run within the sites; many devices that will happily speak OSPF or EIGRP won't be quite so happy participating in an iBGP mesh. And choice A...well, I think we all know the pitfall with choice A, so enough said on that score). Curious to hear the actual mechanism you'd use to make this work in the real world. Thanks! Matt