EIGRP Explained | Step by Step

Summary

This video provides a comprehensive overview of Enhanced Interior Gateway Routing Protocol (EIGRP), developed by Cisco as an open standard. It highlights how EIGRP, an advanced distance vector protocol, forms neighbor relationships through simple hello messages, unlike OSPF's complex mapping. The video explains the process of exchanging routing information using Reliable Transport Protocol and calculating best routes based on metrics. Key concepts like successor and feasible successor routes are introduced, showcasing EIGRP's efficiency in route selection and quick convergence. Overall, it emphasizes EIGRP's simplicity compared to OSPF while acknowledging OSPF's dominance in dynamic routing.

Takeaways

• 😀 EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco-developed protocol that is now an open standard.
• 🔄 Unlike OSPF, EIGRP is not as widely supported by third-party vendors.
• 🌐 EIGRP is designed for use within a single autonomous system as an advanced distance vector protocol.
• 🔗 The protocol uses a three-step process: establishing neighbor relationships, exchanging routing information, and selecting the best routes.
• 📡 Hello messages are sent every five seconds to maintain neighbor relationships and identify active routers.
• 🔍 EIGRP employs Reliable Transport Protocol (RTP) for message delivery, rather than UDP or TCP.
• 📏 Metrics in EIGRP are calculated using a formula involving bandwidth and delay, which can be influenced manually.
• 🏆 A successor route is the best route selected based on the lowest metric, while a feasible successor serves as a backup route.
• 🔄 EIGRP allows for both equal-cost and unequal-cost load balancing among multiple routes.
• ⚠️ EIGRP's ability to quickly converge with minimal downtime is a significant advantage over some other routing protocols.

Q & A

What is EIGRP and who developed it?

EIGRP stands for Enhanced Interior Gateway Routing Protocol. It was developed by Cisco and has since been released as an open standard.

How does EIGRP differ from OSPF?

Unlike OSPF, which builds a complete map of the network to choose the best routes, EIGRP operates using a method where routers only exchange information with their immediate neighbors.

What is the main purpose of EIGRP?

The main purpose of EIGRP is to learn the best route to any given subnet within an autonomous system.

What protocol does EIGRP use for sending messages?

EIGRP uses a Reliable Transport Protocol (RTP) to send routing information updates instead of UDP or TCP.

What is the role of hello messages in EIGRP?

Hello messages are used to establish and maintain neighbor relationships between routers running EIGRP. They are sent every five seconds by default.

What is the significance of the K values in EIGRP?

K values are used in metric calculations for EIGRP and must match on both routers to form a neighbor relationship. The default K values are bandwidth (K1) and delay (K3).

What happens during route recomputation in EIGRP?

When a link goes down and there are no backup routes, the router enters an active state, sends out queries to its neighbors for alternative routes, and tries to find a loop-free route to the lost subnet.

How does EIGRP determine the best route to a subnet?

EIGRP determines the best route by calculating metrics using a formula that considers bandwidth and delay, resulting in a feasible distance that is compared against reported distances from neighbors.

What is the difference between a successor route and a feasible successor route?

A successor route is the primary route with the best metric, while a feasible successor route is a backup route that can be used if the successor fails.

How does EIGRP handle multiple equal-cost paths?

EIGRP can load balance traffic across multiple equal-cost successor routes and also supports unequal load balancing with proper configuration.