Tag: Enhanced Interior Gateway Routing Protocol

The EIGRP Packet Header

VersionOpcodeChecksum
Flags
Sequence
Acknowledgement
Virtual Router IDAustonomous System (AS)

Believe me or not, aside from passing an exam there is another important reason why you should know what is inside the EIGRP packet header. Any hypothesis?

The Job Interview

You thought you know everything when you got the Cisco professional level certification but what happens when the interviewer asked you about what is inside the EIGRP packet header? You memorized all the configurations commands. You know what is BGP route reflector. You know how to do unequal load balancing in EIGRP. You even know how to configure fabric path, ASA firewalls, and do site-to-site VPN. You know everything you did in your laboratory but you forgot what is inside the EIGRP packet header.
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EIGRP Tables and Functions: The EIGRP Neighbor Table

EIGRP like OSPF has three tables: Neighbor, Topology and Routing tables. However, don’t be confused because not all EIGRP tables have the same built like OSPF.

The neighbor, topology, and routing tables are very important in implementing and troubleshooting EIGRP. I often neglect the topology and routing table before because what is important to me is that all neighbors are up. But this is not the case most especially if you want to progress your learning to higher Cisco certification level.

Let’s start with the neighbor table.

If you want to know whether you have established adjacency with neighboring EIGRP router and also to know the uptime, then you go to the neighbor table.

show ip eigrp neighbor
Neighbor table: show ip eigrp neighbor

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IGP: Enhanced Interior Gateway Routing Protocol (EIGRP) Overview

Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary protocol. It uses It is a hybrid protocol because it has features of the Link State and Distance Vector routing protocols. Confused? If you’re new with IGP, it is natural. You are not alone. There are millions to billions of people around the world who doesn’t know what the heck is EIGRP.

EIGRP is Cisco’s baby. It works on all Cisco devices. It is an advanced distance vector routing protocol that has some link state features. Like RIP, it has the hop count feature. Routes that reached the maximum hop cunt will be tagged as unreachable. Although it is not used as its metric, it limits the EIGRP AS when routing to a remote network. The default hop count is 100 and the value can vary between 1 – 255. And, like OSPF it does not send the whole routing table when there is a routing change. (more…)

Difference Between Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP)?

When I first heard about Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP), I was just like, “what on bits and bytes are these?” If you are new to networks and you suddenly heard these on your first day, you might ignore the meaning and also the importance. However, you don’t have to memorize the meaning because you will know it by heart as days go by. (more…)