What is EIGRP? | Understanding Enhanced Interior Gateway Routing Protocol

If you need a quicker and improved way to send data around your network, EIGRP might be the answer. It’s a better version of an older protocol called IGRP, which Cisco Systems made.

It takes the best parts from two types of routing methods, making it faster and more dependable, especially for extensive networks. In this article, we’ll learn about what EIGRP is, how it works, and the tables it uses to keep your LAN running well.

What is the EIGRP Protocol?

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Getting to Know EIGRP: A Quicker and Better Routing System by Cisco

EIGRP, which is the Enhanced Interior Gateway Routing Protocol, is a better version of the old IGRP protocol from Cisco Systems. It blends the good parts of link-state and distance vector protocols, which are ways routers talk to each other.

While it still uses the same basic idea as the old protocol, it’s much faster and can handle more extensive networks. It does this by doing some math differently. Instead of just copying it, EIGRP multiplies it by 256.

The Features of the EIGRP Protocol

The Enhanced Interior Protocol is a routing method that uses a more significant metric (32-bit) compared to the Interior Gateway Routing Protocol (IGRP), which only uses a 24-bit metric. This allows it to make better choices about how to route data and handle more extensive networks more effectively.

A cool thing about it is it can change or divide information into 256, which makes it simpler for networks that have both EIGRP and IGRP to talk to each other. However, an old one can only skip up to 255 times, while this can skip up to 224 hops. So, it can deal with more extensive LANs more efficiently than the others.

It has some cool stuff that the others don’t have, like supporting Variable Length Subnet Mask (VLSM) and route summaries. It also has features found in other protocols like OSPF, such as sending only part of the updates when things change and being faster to adapt.

Similar to the old one, it only shares route table info with nearby routers. This keeps network traffic low and makes sure it stays safe. In short, It is a robust and adaptable method that’s great for managing big and complicated networks.

The Tables of Enhanced Interior Gateway Routing (EIGRP)

This network communication system uses three tables to keep track of route information in a LAN: the Neighbors Table, the Topology Table, and the Routing Table.

1. Neighbors Table

The Neighbors Table helps keep tabs on other routers nearby that are connected to the same network. It finds these neighbors by sending out greeting messages called Hello packets to a particular address.

After finding the neighbors, a reliable way is used to make sure updates about routes and info are sent accurately and on time.

2. Topology Table

The Topology Table holds details about how the network is set up, like all the routes to a place, how far away they are, and which neighbors help get there. It uses something called DUAL (Diffusing Update Algorithm) to figure out the best way to go somewhere.

This algorithm stops loops in the network and quickly adjusts if the network changes.

3. Routing Table

The Routing Table keeps track of the best ways to reach all the places in the network. It picks the best path to a place by looking at its cost, which considers things like how fast the connection is, how long it takes, and how reliable it is.

The Route Table gets updated regularly using info from the Topology Table.

To sum up, the EIGRP protocol is a trustworthy and fast route method. It figures out how to send data quickly and accurately by finding neighbors, understanding the network layout, and picking the best way to go. It’s made for IP networks and is used a lot in extensive business networks.

What is the difference between EIGRP and IGRP?

The big difference between EIGRP and IGRP is in how they measure distance. This protocol uses a more significant number (32-bit) than (24-bit), which helps it make more intelligent decisions about routing and better handle more extensive networks.

Also, the EIGRP protocol can skip up to 224 hops, while others can only skip up to 255 times. This means it can handle more extensive networks more efficiently than others.

What is the Diffusing Update Algorithm (DUAL)?

It uses something called the Diffusing Update Algorithm (DUAL) to find the best route. DUAL looks at things like how fast, reliable, and busy each route is and then identifies which path is the best.

It also keeps an eye on the network for any changes, like if a route stops working or a new one shows up, and quickly finds a new best route if needed. This makes it a robust and flexible way to handle big and complex networks.


To sum up, EIGRP is a solid and effective way to route data made by Cisco Systems. It takes the good stuff from both link-state and distance vector methods to make data move faster and more reliably in extensive networks. With its 32-bit metric, it can make smarter routing choices and handle more extensive networks better than others.

Also, EIGRP uses the Diffusing Update Algorithm (DUAL) to adjust fast to network changes and pick the best path for sending data. It uses tables like the Neighbors, Topology, and Routing Table to manage extensive networks well. So, for businesses needing a quick, safe, and effective way to route data, this networking communication method is an excellent option.

If you want to learn more about how PCs communicate in a network using a different routing method, read our article What is the RIP protocol? It talks about Routing Information Protocol, which is often used in small networks.

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