OSPF and EIGRP running over the same WAN interfaces

[dabonilla]

Hi all,

I'm the new network administrator at my job, since most of the routers are CISCO devices, the network is running EIGRP at the CORE and Distribution.

As a requiriment, I need to change de EIGRP to implement OSPF.

We have 4 Nexus 7000s por CORE and DIST, at border we want to run both OSPF and EIGRP.

My question is,

which is the better approach to achieve my goal - eliminate EIGRP at the CORE and DIST.

What I want to do is:

1- Run OSFP over the same EIGRP WAN interfaces without announcing the LANs, only the WANs and a new Loopback interface which will be configured on each router.

DOUBT: Will Adjacencies be formed without affecting EIGRP neighborships? Will the CPE be hooked by the routing protocols?

But I'd like to know if there any better idea.

Any comment will be appreciated.

[Mark Mc Nicholas]

Hi Dabonilla,

Congrats on the new network admin job.

So your question is a little vague to say the least, However some of the following may help.

Assuming you learn all the same prefixes from your provider by ospf as you do by eigrp then you should be able to to turn on ospf on the wan interface and EIGRP will continue working until you turn it off. This is because EIGRP has the lower Administrative distance (90) where as OSPF is 110. Where they may be a problem is if you learn prefixes over ospf that are not present in your EIGRP adjacency because then they will get inserted into your routing table!

As for not wishing to advertise your lan ranges out the Wan link(s) there are a few ways however just putting the wan links into a difference ospf process is probably the safest way I can think of. You could then use a distribution list/route map to filter if you did need to redistribute routes in the future.

Without more detail I can only provide these insights however I hope they help

you may wish to read which discusses multiple ospf processes. 

https://supportforums.cisco.com/discussion/10691656/multiple-ospf-processes

If this hasn't helped you or you need more information please provide some more details as my current ideas are based upon the very limited info you have provided in your question.

Best of luck 

Mark