OSPF over GRE tunnel?

[Keith9]

I was wondering if there is a way to do this all one one X450G2. Currently at one of our sites we needed to squeeze in an intermediate device, a Cisco 2901 router to terminate a GRE tunnel, and then from that 2901 router, establish OSPF adjacency to a X450G2.

A year later we are bringing up a new site, an d a few things have changed in a years time. For instance, the site last year is still up and running on EXOS 22.5.1.7. The new site's X450G2 switches shipped with 22.6.1.4, but I see there is 30.2.1.8 out now (that I have not yet tried).

The problem I see relates to the configure ospf command itself. The command configure ospf add ? returns a few options, none of which are . Because I can not tell EXOS to apply or "turn on" ospf on that particular tunnel.. it never works. I applied it to the VLAN of course where the tunnel originates, but that does not work.

On the contrary, Cisco IOS has no problems establishing OSPF adjacencies across GRE tunnels. Example code would be this:
interface Tunnel6
description LTE TUNNEL TO R BRANCH
ip address 192.168.205.37 255.255.255.252
ip mtu 1400
ip tcp adjust-mss 1360
ip ospf authentication message-digest
ip ospf message-digest-key 1 md5 7
ip ospf cost 12
tunnel source 10.200.0.5
tunnel destination 10.200.0.21

router ospf 1
router-id 192.168.255.30
network 192.168.205.36 0.0.0.3 area 0


At our new site I want to avoid using up yet another rack unit of space, another power outlet, and another device to manage. I opened up a GTAC case on this since I'm still having trouble with EXOS 22.6.1.4.

[Keith9 · Accepted solution]

GTAC support could not get OSPF to work over a GRE tunnel. They submitted it as a feature request.

To accomplish our needs we purchased an inexpensive but rack mountable Ubiquiti EdgeRouter 4. The Ubiquiti terminates the GRE tunnels, and also advertises OSPF over it. It advertises OSPF back into the /30 transport network we built between the X450G2 switch stack and the EdgeRouter 4.

It works very nicely, and we tested failover and failback. Not bad for less than $200 with the rack mount kit. If your cheap and don't care about rack mounting, you can get the EdgeRouter X for right under $60. That works too... that's what we used initially for the proof of concept prior to spending more on the EdgeRouter 4. Thats only because a coworker owned an extra one that he lent us for the initial test.