Basic concepts of EIGRP or Dynamic Routing.

Dynamic Routing:

Today we try to learn about dynamic routing EIGRP. It is good to remember that CCNA testing involves a simulation with EIGRP. So EIGRP is very important for CCNA testing.

Basic concepts of EIGRP:

EIGRP is an end-to-end gateway routing protocol. This is a protocol that actually features the link-state routing protocol and again it contains many features of the Distance Vector Routing Protocol. With this in mind, the EIGRP is called the Hybrid Routing Protocol. Now the question is what is the Distance Vector Routing Protocol and the link-state routing protocol? By means of the Distance Vector Routing Protocol, the router learns about the neighbor's router on the network and the location of all routers, ie the distance to which the routers are located. And through link routing, you can find out the troubles of each link and select the best.

The benefits of EIGRP are:

1. Supports CIDR and VLSM

2. The EIGRP places a backup path on the topology table so that any problem with the path communicates with the backup path.

3. Determines the value of each router using the DUAL (Diffusing Update Algorithm).

4. The default hop count is -100

5. Send hello messages to neighboring routers. The answer to that hello message is to know which router network is active. This results in faster convergence.

Let's see how the EIGRP works?

First, let's try to learn about EIGRP packets

1. Hello - This packet creates a relationship with the neighboring router.

2. Updates - Updates are used to send updates to the routing table.

3. Query - If there is a problem with the main route, the query sends a packet to know if there is a backup path.

4. Replay - If a neighbor router provides backup path, replay message provides.

5. Reconciliation - Receive the packet through the Reconciliation packet.

Let's see how the route updates ?

The EIGRP is configured on two routers. Let's see what happens with the router turned on.

Step-1: Router-1 will send a Hello message to Router-2

Step-2: On receiving Router-2 Hello message, he will send a Hello message to Router-1

Send router update packet with router-2 to router-1 

Step-3: Route-1 will receive an update packet as well as send an Acquilage message to Router-2. This is how the EIGRP protects its neighbor's routers.