Enhanced Interior Gateway Routing Protocol (EIGRP)

Enhanced Interior Gateway Routing Protocol (EIGRP) is a routing protocol designed to help automate routing decisions and configuration. Below are some detailed aspects of EIGRP:

1. Basic Functionality:

   • EIGRP is used to share routes with other routers in the same autonomous system.

   • It supports both IPv4 and IPv6, and can route multiple network-layer protocols

   • IPV4 Multicast address : 224.0.0.10

   • IPv6 multicast address is ff02::a

2. Protocol Type:

   • EIGRP is an advanced distance-vector routing protocol, which combines features of both distance-vector and link-state protocols.

   • also, called as hybrid protocol.

   • it functions like a distance-vector protocol by sending routing updates to neighboring nodes but also integrates the rapid convergence and loop-free path calculation features of a link-state protocol. This is achieved through the Diffusing Update Algorithm (DUAL), which determines the optimal route.

3. Key Features:

   • Rapid Convergence: EIGRP has fast convergence times due to the DUAL algorithm. It quickly recovers from network changes or failures without waiting for periodic updates.

   • Efficient Use of Bandwidth: EIGRP sends updates only when there are topology changes rather than at regular intervals. It also uses multicast to send updates, minimizing unnecessary network traffic.

   • Load Balancing: It supports equal and unequal cost load balancing, providing flexibility in traffic management.

   • Allows assigning different weights to each server based on their capabilities, means some servers might receive more traffic than others depending on their capacity.

4. Route Types:

   • Internal Routes: Routes that originate from within the EIGRP autonomous system.

   • External Routes: Routes that are imported into EIGRP from other routing protocols or external sources.

5. Metrics:

   • EIGRP uses a composite metric based on bandwidth, delay, load, and reliability to choose the best path. The default metric calculation focuses mainly on bandwidth and delay.

6. Configurability:

   • Network engineers can configure EIGRP with various features, such as route summarization, stub routing, and authentication for security.

7. EIGRP Process Flow:

   1. Neighbor Discovery: EIGRP routers exchange Hello packets and establish adjacencies.

   2. Route Advertisement: Neighbors share routing information through EIGRP update packets.

   3. Topology Table Update: All received routes are stored, and DUAL determines the best loop-free paths.

   4. Best Path Selection: The successor (best route) is selected and placed in the routing table.

   5. Routing Table Update: The chosen prefix is installed and used for forwarding traffic.

Basic EIGRP lab

EIGRP Neighbor Table

EIGRP Topology Table

Routing Table