As always... "it depends." It depends on the size of you WAN: # routers and # of routes. OSPF is more scalable, but you can summarize anywhere in EIGRP, not just at ABRs. Supposedly, EIGRP v6 is supposed to be more "area-like" in the future. Also, consider that OSPF works with MPLS.
How big is or will be your network? Will you need or want to run MPLS TE in your network? Will you have a Cisco-only network?
I would use OSPF in any case.
Hope this helps.
EIGRP has a general maximum of 400 adjancentcies. I have had networks up to around 600 adjancentcies, but if you have multible core routers; more than 400 will cause the network to flap if a router goes down.
I would strongly recommend OSPF over EIGRP. Because of the following:
1. better convergence over wan link
3. more tunable parameter in OSPF as compare to EIGRP
I created a new thread: Follow up Question: EIGRP vs. OSPF. If you have thoughts, I'd like to hear them! Thought a new thread would highlight the question, since this thread is kind of old.
Back those days when I had to route IP, IPX, and Apple Talk, EIGRP was good choice. Now with IP centric environment, OSPF is the way to go if you want to have the flexibility of optimizing your huge network.
If you want to convert to OSPF from EIGRP in a huge complex network, be sure to have modems connected to all major routers.
In any hub and spoke environment (including the use of IPSec tunnels), you want to be able to limit the propagation of information to the spokes (as they really only have one exit). Either protocol offers mechanisms to limit the information transmitted to the remotes.
A hub-and-spoke topology is probably the only one in which EIGRP has a slight edge over link state protocols. In a link state protocol, there's always the issue of how many areas can the hub support vs how many remotes in an area -- because of the synchronization issues in an area.
The real question you want to ask yourself is "why?". Why do you want to migrate from EIGRP (into anything else)? Are there features or applications that cannot be supported by EIGRP?
In general, we try to keep parity in protocol features -- which means that you should be able to use your favorite protocol. ;-)
If oyu want to talk specifics, pls feel free to contact me directly.
Being an EIGRP user myself, I have appreciated the ability to summarize at any given point in my network, as well as being able to limit the query range in EIGRP with summarization and/or EIGRP stub features. Also, Cisco is constantly improving EIGRP as networks grow and get more complex. A recent example of this is the recent fix for the SIA timer and neighbor resets.
IMHO, I really think a well-designed EIGRP network can be VERY scalable. The only thing I wish EIGRP had (but cannot ever have, given the nature of the protocol) is the concept of a DR and BDR. On Ethernet segments, a lot EIGRP routers can create some complexity in troubleshooting.
Finally, for all other posters and readers, the postings by aretana are the ones to pay attention to. Alvaro, Russ and Don are the guys that pretty much wrote the book (literally) on EIGRP at Cisco. I had a very enlightening Networkers session with Don this year. These guys know their stuff!