Two More Perspectives on EIGRP

I’d like to share with you two perspectives in response to a previous post on EIGRP vs OSPF. They are both thoughtful and well-stated, so I’ll share them without comment.

The first is from my pal Eddie Parra, who disagrees with my statement, “SIAs should not happen even in very large networks, but once again because you don’t have to think much about growing EIGRP topologies you can get yourself into a situation where they do in fact occur.” (Italicized emphasis is Eddie’s.)

While I agree with most of your EIGRP statements, I have to disagree with this one.  I personally think EIGRP customers have to think more because query boundaries need to be well thought out.  Query boundaries are the allusive factor in EIGRP scalability, which are not as clearly define as OSPF areas.  Without establishing query boundaries, a lost prefix will cause queries throughout the entire network.  Often EIGRP (Enterprise) customers relate route summarization and distribute lists to route reduction, not query boundary establishment.  This only gets worse as EIGRP (Enterprise) customers realize that modern routers are not the CPU/Memory starved little boxes they once were.  Another factor of magnitude in these scenarios is unnecessary redundancy in topologies, which is often quite devastating (e.g. Two 6500's with 50+ VLANs and EIGRP neighbor adjacencies for every one).

The other comment comes from Mike Morris:

Having worked on very large corporate networks (Fortune 10) I've had experience with OSPF and EIGRP in large, multi-national networks. As a pure routing protocol, I like EIGRP more because of the control it provides. Enchaned routing metrics (delay and bandwidth) and particularly interface route filtering can be SOOOOO helpful. Plus, the troubleshooting tools and routing algorithm are easier to understand (for me at least) than the OSPF database monstrosity. OSPF lacks these features.

However, OSPF has two features that often make it a better choice (as Jim mentioned). First, if you do not configure EIGRP correctly from the start and let it get out of control, it will hurt you. Now, this is really more about good architecture, templates, and standards, but we all know networks exhibit entropy. If you have a problem being ruthless with your network design, then OSPF is easier. It will incorporate your bad design better than EIGRP will. Second, with more devices routing these days (FWs, App Acceleration, other vendors), OSPF just makes more sense. We do OSPF with our FWs right now and it makes our Internet design work much better. Not even having the option of routing protocols because you use EIGRP can limit your options in the future (do PIX even support EIGRP yet???).

So, if I had my ultimate pick the best "routing" protocol, I like EIGRP, but the intelligent business decision is often OSPF.

Thanks, guys!

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