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Unanswered Question
May 20th, 2008
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Guys a quick one what why would we use EIGRP over OSPF....i know few things like convergence is faster what would be the otehr reason to use eigrp over ospf....secondly how many routers can eigrp support like igrp if i m not wrong can do up to 255? regards

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shiva_ial Tue, 05/20/2008 - 04:05
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Hi Guroo,

EIGRP has multiprotocol support , i am not sure on eigrp but ospf scales very well with only 40 routers in an area as an best practise.

i believe eigrp can support more than 40,since it doesn't contain areas.

royalblues Tue, 05/20/2008 - 04:07
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The Choice actually depends on the network topology.

Both the routing protocols provide fast convergence and scale pretty well. EIGRP is certainly faster than ospf when there is availability of a feasible successor. It also works out well when the topology is confined to one geographical location whereas OSPF works out well where the topology is more heirarchial (using multiple areas).

Eigrp is also easy to setup than OSPF

EIGRP is limited to an hop count of 255 (100 by default)


lamav Tue, 05/20/2008 - 05:22
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Another thing to consider is the fact that OSPF is an open standard and is compatible with all manufacturer routers, not just Cisco. So, in a mixed environment, OPSF may be the way to go.

Richard Burts Tue, 05/20/2008 - 07:28
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Each protocol has certain things in which it is better. Some other aspects to consider where EIGRP has some advantages over OSPF:

- while OSPF is very restricted on where you can summarize routes (summarization is only allowed on ABR and ASBR) EIGRP will allow you to summarize anywhere in the network that you want to.

- while OSPF does not have much ability to filter routes once they are in the OSPF network, EIGRP allows you to filter routes at any part of the network where you want to.

- while OSPF does not allow you to alter the metric of any route once it is in the OSPF network, EIGRP will allow you to alter the metric of a route by using offset lists.

- EIGRP has the ability to configure a router as an EIGRP "stub" while OSPF does not have a capability like that.



tj.mitchell Tue, 05/20/2008 - 08:10
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It depends on the network topology, OSPF scales well to large to very large network deployments, plus is a standard. EIGRP is nice for small to large deployments very large if designed properly but is Cisco only. But usually depends on the client and network topology.

Either way will work, just implemented different ways and the design and topology needs to take this into account.


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