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i have undersatnding of both of routing protocols....but confuse abt one thing.......what is themain difference why would we choose ospf over eigrp or why would we choose eigrp over ospf????? which is more faster.......can someone please explain



you can not comapre those protocol,ospf is a link state protocol , eigrp is between distance vector and link state so it is a hybrid, eigrp is proprietary, ospf is a standard so it can operate in a mixed enivrenment of many router from different vendors, eigrp is faster than ospf when it comes to convergence but cannot operate in a router from others vendors.

both of them are not plug and play you need a good desing before implementing them so that you can take advantage of the summarization that they offer and the many others features.

both run different algorithms to find out the best way to go to a destination ospf SPF,, eigrp dual.

so as result the only heavy diffrence between them (open standard, proprietary)!!!


do rate if it does clarify



(1)The biggest difference is that OSPF is multi vendor compatible and EIGRP is Cisco properity.

(2)The convergence time for EIGRP is less then OSPF which makes it the best of the two.

As the previous posts have pointed out one important difference is that OSPF is standards based and supported by many vendors while EIGRP is proprietary. So sometimes the choice of protocol is dictated by what equipment you will be using. (Also note that not all Cisco equipment supports EIGRP - the VPN concentrators and the PIX-ASA can run OSPF but not EIGRP.)

I will take a slightly different position than Jaideep about the speed of the protocols. In some cases (especially where there is a Feasible Successor) EIGRP is certainly faster than OSPF. But in other situations (especially if EIGRP has to transition to the active state, query neighbors, wait for responses while query propagates through a large network) OSPF will be faster. What really matters is that both protocols scale pretty well and both protocols converge quickly.

I believe that sometimes the topology of the network will affect the choice of protocols. I had a customer at one point who had a network that spanned multiple states. In each state there were a number of small offices who communicate with each other through a regional office. The regional offices had redundant WAN connections to HQ. Most data traffic was contained within the state or was to HQ (there was little state to state traffic). Even though their network was all Cisco routers and EIGRP was a possibility it seemed that the hierarchial nature of their network fit OSPF better (multiple stub areas).

You might also choose the routing protocol depending on how you intend to do route summarization. OSPF puts constraints on doing route summarization (summarize on ABR for inter-area routes and summarize on ASBR for external routes - no other places where OSPF can summarize) where EIGRP can configure summarization on any interface of any router in the network.

Another aspect to consider is whether there is a need to filter certain routes so that they appear in some parts of the network but not in other parts. That is very difficult in OSPF and easy in EIGRP.

So there are a number of factors to consider when choosing a routing protocol for a particular implementation.





EIGRP is currently being coded for the PIX-ASA.

The way the convergence times generally work out are:

-- OSPF within an area, about 200ms, with good tuning, etc.

-- EIGRP with an FS, about 10-20ms.

-- EIGRP with no FS, single query hop, 200ms.

-- EIGRP with no FS, two query hops, 400ms.

These are, of course, very rough, and depend on your routers, etc.

Network design is the key in all cases.



whats the diff between LSA tye 3 and LSA type 4 in ospf


The type-3 LSA is generated by ABRs in order to propagate information about intra-area routes from one area into the other areas to which it connects.

The type-4 LSA is generated by each ABR in order to inform all attached areas about the location of ASBRs in the other areas it connects to.


PS> Pls do remember to rate posts.

Thanks Paresh