OSPF implementation on Core Switch

[CiscoPurpleBelt]

So let's say I have just 2x Cat4k or 6k that I would like to enable OSPF between (one acts as Core switch where routing for access switches is done and other will be used for access and a bit of a backup, therefor won't be configured for HA) , is it probably best to keep it simple and do ospfv2 point2point since only have 2 switches and don't really plan on scaling adding more and running OSPF?

Perhaps just do OSPFv2, enable it on port-channel between them. I don't see much benefit of using OSPFv3 if dynamic routing is done between only 2 switches right next to each other. 

What if I added more devices to join to OSPF in future, such as adding another 4k or something then configuring those in HA and enabling OSPF, would it be best to just do OSPF broadcast now?

Any suggestions, advice?

[Richard Burts · Accepted solution]

If the switches are connected by Ethernet then the simple thing is to use the defaults and let the OSPF operate as a broadcast connection. I do not see much advantage in changing it to point to point.And that makes it easier down the road if you do add another switch.

[CiscoPurpleBelt]

Thanks again Richard. What do you think about using OSPFv3 in this type of case now (small OSPF doman; 2 or so devices), so would it matter much or is it probably just better to go ahead and do OSPFv3 anyways. Perhaps even use the more secure means of authentication it provides with IPSEC especially if more devices begin to join?

[Georg Pauwen]

Hello,

in addition to Richard's remarks, what role does OSPFv3 play here ? Are you running an IPv6 network ?

[CiscoPurpleBelt]

No not at this point. If that is not going to be implemented at least anytime in near future, would you bother with a small OSPF domain?

[Richard Burts · Accepted solution]

The main motivation for implementing ospfv3 is its support for ipv6. If you are not planning to implement ipv6 then my advice would be to just implement ospfv2.

If you are connecting 2 switches there might be some consideration of whether to implement a dynamic routing protocol or whether to just use static routes for the remote subnets. One argument is that static routes are more simple and do not use up network bandwidth. But I would suggest that if there is more than 1 path connecting the switches then a dynamic routing protocol provides the ability to adapt to a failure of one link. And especially if there is a possibility or more than 2 devices I would suggest that a dynamic routing protocol is the better alternative. And for a small network like this ospfv2 is better than ospfv3.

[CiscoPurpleBelt]

Yes dynamic routing would be what I would have in mind. 

Tracking on v3, thanks again Richard!

[Richard Burts]

You are welcome. I am glad that our suggestions have been helpful. Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.