DMVPN Routing Protocols

[Darren Hunter]

Hi all, I have a couple of questions about routing protocols over  DMVPN.

I'm a bit rusty so I'd appreciate if there's mistakes in my understanding if you could correct me.

I understand the EIGRP doesn't ordinarily use the next hop field, receiving routers insert the source of the EIGRP update as the next hop. It uses split horizoning and feasibility tests to detect loops. Over DMVPN you can use the no ip next hop self eigrp command to force eigrp to insert the originating router as the next hop.

OSPF you can specify different OSPF network types - I cannot remember exactly but it may be broadcast networks or multi-access that don't change the next hop?

RIPv2 - I do not understand how RIPv2 works with DMVPN (although I know it does) as to my knowledge Ripv2 does indeed change the next hop.

Can anyone explain how Ripv2 integrates with DMVPN and confirm or correct my understanding of EIGRP/OSPF?

Thanks very much

[ghostinthenet · Accepted solution]

You're correct on EIGRP. OSPF preserves the next hop of the originating router in all modes except point-to-multipoint. RIPv2 always preserves the original next-hop and this can't be turned off... so it works with DMVPN with no modification except for the split-horizon considerations.

For scaling DMVPN, your worst choice is OSPF because of the large link-state database that forms with so many routers on a single subnet. EIGRP and RIPv2 are very good for DMVPN because the updates are small and simple. These days, I'm moving to BGP for just about all of my DMVPN work... mostly because it scales better than any IGP.

[Darren Hunter]

Hey, thanks for the response that's cleared everything up for me :)