EIGRP vs OSPF

[router_duchess]

Recently non-Cisco devices have been placed as VPN Edges in the spokes of our network over the WAN to satisfy Legislation regarding data security. Currently the Infrastructure is running EIGRP, but the new vendor devices support OSPF. Is there a design advantage that OSPF has over EIGRP that might warrant a change in routing protocol to make use of the non-Cisco edges routing functionality?

[bhatia.sachin]

I dont c any advantages that OSPF has over EIGRP in ur network.The spoke routers can be configured as stub in both protocols to limit their database size.Transition to a new protocol would require good design an careful planning unless u think of redistribution which might unnecessarily burden ur spoke routers.

The only advantage with OSPF can be considered its various LSA types which are greatly helpful in troubleshooting.

[ankurbhasin]

Hi Router,

Yes there are certain advantages running ospf over eigrp.

First and very imp it is an open protocol which means can run on any non cisco devices.

Second which is another good advantages is that ospf is that while you implement ospf you can configure your devices into certain areas like area 0 and area 1 and like that and as per your network and geographic conditions you can have many areas and now any problem like link flap and anything happeneing to the devices which only affect the network in that particular area and not the whole network but in EIGRP is something is happeneing to a link or devices for long time can disturn the whole network.

One thing I like about OSPF, even in a 100% Cisco network, is the fact the network is set up in areas. The effects of 'troubles' in one area are contained, thus does not cause unneccessary router computation in the other stables areas. EIGRP does not offer this.

I will say OSPF is sweet and stable and good routing protocol for big and complex network which includes multivendor products.

HTH

Ankur

[ruwhite]

"One thing I like about OSPF, even in a 100% Cisco network, is the fact the network is set up in areas. The effects of 'troubles' in one area are contained, thus does not cause unneccessary router computation in the other stables areas. EIGRP does not offer this."

EIGRP doesn't offer areas because it doesn't need to. Areas are constructs specifically designed to constrain flooding (which is the primary scaling limitation of OSPF), and EIGRP doesn't flood. Instead, you use aggregation, in combination with the network's topology, to divide the network up, logically, in EIGRP.

Note that areas can actually be a constraint on network design in OSPF--with OSPF, you can only aggregate and filter routes along an area border. In EIGRP, you can aggregate route anyplace it makes sense, topologically.

Each protocol has its positive points, and each protocol has its negative points--look at the "Which Routing Protocol?" appendix in the new Cisco Press book _Optimal Routing Design_ for a complete look at what they are. There's too many considerations for this short space.

:-)

Russ.W

[joyride_us]

HI,

I happen to be a big fan/user of EIGRP mainly because it uses way less resources in the router and therefore allows me to purchase smaller/cheaper routers.

However, I lately discovered some great points about OSPF over EIGRP(I am interested in feed-backs on those points) :

-there is no such thing as external OSPF whereas External EIGRP exists with a really bad AD (I don't think that the AD of Ext-EIGPR can be changed) : bad luck, those external routes are those I wanted the packets to take, over RIP routes for example but even RIP has a lower AD than ext EIGRP : good morning headaches!!OSPF is AD 120 what-so-ever which, in addition, can be changed!

-the set-metric command in a route-map does not work with EIGRP but it works with OSPF. Very useful command though! From this site :

set-metric : Metric value; an integer from -294967295 to 294967295. This argument applies to all routing protocols except Interior Gateway Routing Protocol (IGRP) and Enhanced Interior Gateway Routing Protocol (EIGRP).

EIGRP remains a very good protocol with many features like unequal-cost load-balancing, simple configuration, love it : but next time when designing a solution, I will think twice!

Hope this helps!

Good Luck.

[paddyxdoyle]

Hi,

You can change the AD of EIGRP

I think the command is:

myrouter(config-router)# distance eigrp

HTH

PJD

[joyride_us]

Good stuff!

Thanks

[ruwhite · Accepted solution]

"There is no such thing as an external in OSPF, while there is in EIGRP."

Actually, both protocols have external routes. EIGRP uses admin distance to prevent routing loops between EIGRP and other protocols when redistributing between those protocols. OSPF doesn't, because it's a link state protocol. As long as loops don't form, it doesn't matter which method is used. Note that all internal routes are preferred over all external routes within OSPF itself.

Set metric is sort-of a misnomer in EIGRP, since there are five metrics, only two of which normally have any impact on choosing the shortest path to the destination. Newer EIGRP code supports the ability to change all the metrics in an EIGRP route through a route map.

Set metric should only set the metric at an ABR or ASBR in OSPF, because setting the metric anyplace else should put you in a position of creating routing loops.

The metrics in OSPF are actually more limited than the metrics in EIGRP. There are no such things as negative metrics in either protocol. If you feel limited by the range of metrics available in either protocol, then you must have a much larger network than any I've ever seen. :-)

In the end, the only real reasons to choose between the two are topology, ease of configuration, network design, and other such factors.

:-)

Russ.W