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EIGRP and OSPF are both IGP protocols, the former is a mostly Cisco protocol and the latter is a well established open standard. What are the benefits of one over the other?

Put another way, when deploying a network, why choose one over the other? If you have mixed devices the choice would obviously be OSPF, but what if you are running a Cisco only shop? Are there any features where EIGRP excels compared to OSPF that would make it feasible to only deploy EIGRP?

closed as too broad by Brett Lykins, SimonJGreen, Peter, Mike Pennington Jan 6 '14 at 11:57

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    Most of the routing books deal with comparision of the link-state and "hybrid" or in this particular situation - EIGRP. Why don't you take a time to read them first? – Łukasz Bromirski May 8 '13 at 21:18
  • While the question is valid and the answering information valuable. I feel that this question as written today is too broad for the Stack Exchange Q/A format. Specifically, asking "What protocol should one choose when deploying a network?" is a question that has many variables and many answers, all depending on the specific situation at hand. – Brett Lykins Dec 31 '13 at 13:49
  • It's more about the choice between EIGRP and OSPF, the title of the question doesn't ask for what protocol to use but asks for a comparison of OSPF vs EIGRP and the benefits of each protocols. So I must disagree. – Lucas Kauffman Dec 31 '13 at 14:21
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    I would agree that the question is not useful. The nerd knob stuff does not matter in 95% of networks, its either I need to run OSPF to talk to non cisco gear or matter of religion where you have all cisco gear. – fredpbaker Jan 3 '14 at 1:59
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    If you can set aside your personal religion, on purely technical merit, they're more-or-less even. However, people are rarely so objective on this particular subject. – Ricky Beam Jan 6 '14 at 8:24
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EIGRP is now an IETF draft so it's no longer proprietary. See http://tools.ietf.org/html/draft-savage-eigrp-01

If we look at EIGRP with default settings and OSPF with default settings and there are multiple loop free paths to a destination then EIGRP will converge much faster because it keeps what are called feasible successors in it's topology database. These are basically loop free alternatives to the best path. EIGRP also has summarization at any point in the network. It also has stub feature which is useful when you don't want to use a router for transit. Commonly deployed in DMVPNS. EIGRP is also less confusing than OSPF because it does not have different network types and EIGRP is easier to deploy in hub and spoke scenarios.

EIGRP uses a flat network without areas, this can both be an advantage and disadvantage.

OSPF is obviously an open standard so it's the logical choice if you have multiple vendors. It can perform well but it requires that you tweak SPF timers because by default in IOS there is a 5 second wait before running the SPF algorithm. OSPF uses areas which means you can segment the network more logically. OSPF can only summarize between areas. OSPF is link state so it has a better view of the entire network than EIGRP before it runs the SPF algorithm. Network administrators will usually be more comfortable with OSPF because it's more commonly deployed.

Both protocols have advantages and disadvantages. But the common answer that EIGRP should be discarded because being proprietary is not entirely true any longer.

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    No longer proprietary but also not implemented by any other companies outside of cisco. So the end result is the same. – Tim May 8 '13 at 19:55
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    It's coming. Not sure which ones but Donnie Savage mentioned that 5 companies or so are releasing products with it. That said I expect it to be companies like Huawei or other asian based companies. Because EIGRP has been proprietary people have been lazy when comparing the two. I compare them technically and for an enterprise EIGRP is not a bad choice. for an ISP I would go with ISIS. – Daniel Dib May 8 '13 at 20:30
  • Just a quick FYI, this was also discussed on Whirlpool recently - forums.whirlpool.net.au/forum-replies.cfm?t=2091564#r10 – OzNetNerd May 9 '13 at 3:43
  • @DanielDib, speaking of IS-IS, why do ISPs favor that over OSPF? In 90 words or less. ;-) – generalnetworkerror May 29 '13 at 8:12
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    > EIGRP is now an IETF draft so it's no longer proprietary. See ietf.org/id/draft-savage-eigrp-00.txt Yep, but: > 1. Advanced features of EIGRP (namely stub areas) will not be released to the IETF. 2. Informational RFC allows Cisco to retain control of the EIGRP protocol. 3. EIGRP is still technically proprietary.<br> > So, the advanced features of EIGRP are not being released – no stub areas, no way to control propagation or logically define areas. No DMVPN topologies that will scale. This is one of the primary reasons you would use EIGRP.<br> More: [Why Is Cisco Bothering With “Op – t3mp Nov 29 '13 at 2:04
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You can read about the finer workings of these protocols for yourself, they are thoroughly documented on the Internet and it's a doddle to find information on them.

From a practicle perspective I would say that in the case of EIGRP vs OSPF, OSPF always wins for the following reasons:

Convergence Speed:

Everyone always mentioned that EIGRP is faster than OSPF using default settings. If you deploy either protocol without reading about them and use their default settings, then you clearly don't know what you are doing in my opinion. Why would you deploy default settings without knowing what they are, and when you do realise what they are you realise that OSPF supports BFD and becomes lightening quick (as does ISIS).

Traffic Engineering:

Because OSPF like ISIS is based on TLV values, it has been extended quite a lot. It has support for extensions like MPLS-TE and GMPLS.

Continual Expansion

As I mentioned above, OSPF and ISIS have been extended quite a lot and extension drafts are being written fairly regularly and will continue to be. EIGRP doesn't have many of the advanced options these two do.

Scalability

OSPF scales better than EIGRP with its use of areas however, I don't think this really matters either (like the convergence time aregument, due to BFD). Not many people are running 10k routes in one area in OSPF. Typically I would use an IGP for fast routing within a given part of a network, but ultimately iBGP carries all the internal routes. Every single router doesn't need every internal route in its RIB sourced via OSPF if you have hundreds or thousands or routers, some of them are so far away (topologically speaking) it's worthless knowing about them.

Interoperability

Lastly there is the obviously reason that EIGRP is/was a Cisco proprietary technology. Although this has recently been submitted into a draft for other software vendors to start incorporating, it's too late (I believe). No currently running network is going to waste huge sums of money switching from some other IGP to EIGRP, and I don't know why a new network would consider it (if you are going to be mixing Cisco equipment with non-Cisco). Simply because non-Cisco equipment that supports OSPF has been doing so for years. The code is tried and test, many bugs fixed, oodles of information on line etc. It will take years for EIGRP to catch up (if it isn't too late already!).

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    I think this answer needs a rebuttal from Donnie Savage. :) – scottm32768 May 8 '13 at 22:14
  • I'm just trying to fill the site with relevant questions I know lmgtfy is very relevant to this topic – Lucas Kauffman May 9 '13 at 5:57
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    This is a great answer, but I have to point out that native OSPF did not employ TLV's, only OSPF-TE (and other OSPF extensions) do/does; OSPF was written/designed explicitly for IPv4. ISIS always did have TLV's, which is why you don't have an ISISv3. :-) See tools.ietf.org/html/draft-bhatia-manral-diff-isis-ospf-01 section 18. – John Jensen May 24 '13 at 7:31
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I would suggest the right answer is it depends on the topology of the network. OSPF requires area boundaries to do summarization, if you are doing a green field network or your topology is condusive to drawing areas out then by all means use it. If your network requires spokes to connect to multiple hubs, then OSPF is harder to do, when I had this requirement on my frame relay network I migrated remote sites to BGP. I wanted to use EIGRP and stub routers but cisco mentioned that more resources were being spent on BGP-OSPF interoperability vs EIGRP-OSPF interoperability so I went BGP on that basis. Another way to put it is that EIGRP with its stub routers and the ability to summarize wherever you want will scale better in a 'messy' topology.

  • I would agree. The more complex one's topology, the more one should naturally gravitate to OSPF. In a simple Cisco-only topology, EIGRP is too trivial a setup to ignore. I've seen many untrained people setup EIGRP networks; I've never seen one setup OSPF. (I recall one massive cluster f*** of an attempt. That story, btw, ended with an NRC fine for disrupting comms to backup control systems.) – Ricky Beam Jan 6 '14 at 8:37

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