Quick question about EIGRP & OSPF

OSPF uses a simple metric based on the sum of the link "cost" to a destination. Cost can be manually assigned or automatically set based on link bandwidth.

EIGRP uses a compound metric based on multiple parameters - bandwidth, delay, load, reliability and Maximum Transmission Unit (MTU). By default, it uses only the bandwidth and delay parameter.

In both cases to obtain the metric for a destination the indvidual link metrics are added together. However see the section lower down regarding EIGRP.

For CCNP you need to be right on top of this. You will need to refer to some decent books or the Cisco web site.

I would say that this was guaranteed to come up in the exam.

I can just see it:-

Of delay, bandwidth, reliability, ... (I forget), some made up.

the default metrics used by EIGRP are:-

A B C

OOPS forgetting is a bad idea since I need to do CCNP now too.

updates contain five metrics: minimum bandwidth, delay, load, reliability, and maximum transmission unit (MTU). Of these five metrics, by default, only minimum bandwidth and delay are used to compute best path. Unlike most metrics, minimum bandwidth is set to the minimum bandwidth of the entire path, and it does not reflect how many hops or low bandwidth links are in the path. Delay is a cumulative value which increases by the delay value of each segment in the path. For more information on EIGRP metrics refer to the Enhanced Interior Gateway Routing Protocol White Paper.

Thanks fellas, I remembered now what I was thinking of. EIGRP uses the lowest bandwidth link in the path to calculate the metric, wheras OSPF uses the sum of the bandwidths. (plus other calculation for both protocols.)

Let be very clear about this - OSPF DOES NOT uses the sum of the bandwidths - it uses the sum of the link costs - the link costs CAN and usually are based on the link bandwidth.

You can set the OSPF link cost by configuring the "ip ospf cost" command on an interface and in so doing give a cost value that is not based on bandwidth but someother factor.

EIGRP updates contain five metrics: minimum bandwidth,

I too can guarantee that it will come up because I just took the

642-801. The intricacies of EIGRP and OSPF easily account for 2/3s of the test. This includes the differences, simularities, metrics, neighbor relationships, scenarios involving successors or DRs failing, etc. I found the IS-IS questions to be fairly simple since I've been reading up on it for my own use for a couple months now. They had a number of questions and a simulation involving redistribution. BGP questions were on the test too, especially pertaining to the involvement between the IGP and EGP, how announces what, etc. IPv6 was also on the test including an in-depth analysis of the header as well as basic functionality. They'll throw a routing table at you and a network diagram and ask "what kind of area is area X". You need to recognize that area X is a NSSA area based on what's in the routing table. They'll give you a network diagram with IP info, tell you that it's OSPF, the configs don't specify a loopback and no router-ID is configured, that everything was just rebooted, and that the IGP has finished it's election processes. They'll then ask you which router is the BDR.

Basically if you aren't very familiar with the finer details of EIGRP (they wouldn't shut up about EIGRP), OSPF, IS-IS, iBGP, some eBGP, some RIPv2 for comparisons, and IPv6 then you need to study some more. This test requires a fair bit of experience and/or lab time.

Good luck J