IGRP vs EIGRP: Key Differences and the Advantages of EIGRP

Introduction:

IGRP (Interior Gateway Routing Protocol) and EIGRP (Enhanced Interior Gateway Routing Protocol) are both Cisco-proprietary routing protocols. IGRP is a traditional distance-vector routing protocol, while EIGRP is a more advanced hybrid protocol that incorporates features of both distance-vector and link-state protocols. This report will discuss the key differences between IGRP and EIGRP and explain why EIGRP is considered an improvement over IGRP.

Key Differences Between IGRP and EIGRP:

  1. Convergence: EIGRP provides faster convergence by utilizing the Diffusing Update Algorithm (DUAL) to maintain feasible successors for quick route recomputation in case the primary path fails. In contrast, IGRP relies on periodic updates and takes longer to converge.
  2. Network Layer Protocol Support: EIGRP supports multiple network layer protocols, including IP, IPX, and AppleTalk. IGRP, on the other hand, supports only IP.
  3. Addressing Efficiency: EIGRP supports Variable Length Subnet Mask (VLSM) and Classless Inter-Domain Routing (CIDR), allowing for more efficient utilization of address space. IGRP does not support these features.
  4. Routing Updates: EIGRP uses partial and bounded updates, reducing network overhead and conserving bandwidth. IGRP sends periodic full routing table updates, which consume more network resources.

Configuration Example:

To migrate from IGRP to EIGRP on a Cisco router, use the following commands:

  1. Enter global configuration mode:

Router# configure terminal

2. Remove IGRP configuration:

Router(config)# no router igrp [AS_NUMBER]

3. Enable EIGRP and configure the autonomous system number:

Router(config)# router eigrp [AS_NUMBER]

4. Configure EIGRP network statements to advertise the desired networks:

Router(config-router)# network [NETWORK_ADDRESS] [WILDCARD_MASK]

5. Save the configuration:

Router(config)# end
Router# write memory

Conclusion:

EIGRP offers several advantages over IGRP, including faster convergence, support for multiple network layer protocols, more efficient addressing, and reduced network overhead due to partial and bounded updates. These improvements make EIGRP a more robust and scalable routing protocol for modern network environments. Migrating from IGRP to EIGRP can help improve network performance, stability, and efficiency.