EIGRP Cheatsheet

Protocol Overview:

  • EIGRP is a Cisco proprietary routing protocol used for dynamic routing within an autonomous system (AS).
  • It is an advanced distance-vector routing protocol that uses features like Diffusing Update Algorithm (DUAL) for fast convergence.
  • EIGRP supports classless routing and is compatible with IPv4 and IPv6.

Key Features:

  1. Advanced Metric Calculation: EIGRP uses bandwidth, delay, reliability, load, and MTU values to calculate the metric for path selection.
  2. Fast Convergence: EIGRP minimizes convergence time by using partial updates and maintaining a topology table.
  3. VLSM Support: EIGRP supports Variable Length Subnet Masking (VLSM) to efficiently use IP address space.
  4. Route Summarization: EIGRP allows summarization of networks to reduce routing table size and optimize routing.
  5. Load Balancing: EIGRP supports equal-cost load balancing, distributing traffic across multiple paths with the same metric.
  6. Neighbor Discovery: EIGRP uses Hello packets to discover and maintain neighbor relationships.
  7. Authentication: EIGRP supports authentication mechanisms to ensure secure routing exchanges.

Configuration Commands:

  1. Enable EIGRP: router eigrp <AS number>
  2. Add Networks: network <network-address> <wildcard-mask>
  3. Enable Auto Summary: auto-summary
  4. Configure Metrics: metric weights <k1> <k2> <k3> <k4> <k5>
  5. Enable Load Balancing: maximum-paths <num>
  6. Configure Authentication:
    • Enable Authentication: authentication mode <mode>
    • Set Authentication Key: key chain <chain-name>
    • Assign Key to Interface: interface <interface> authentication key-chain <chain-name>

Verification Commands:

  1. Show Neighbors: show ip eigrp neighbors
  2. Show Topology Table: show ip eigrp topology
  3. Show Routing Table: show ip route eigrp
  4. Show EIGRP Interfaces: show ip protocols

EIGRP Message Types:

  1. Hello: Used for neighbor discovery and maintaining neighbor relationships.
  2. Update: Conveys routing information and updates to neighboring routers.
  3. Query: Sent when a router needs more information about a route from its neighbors.
  4. Reply: Provides a response to a query message.
  5. ACK: Acknowledgment message confirming receipt of EIGRP packets.

EIGRP Metric Components:

  • EIGRP uses the following metric components for path selection:
  1. Bandwidth: The bandwidth of the outgoing interface.
  2. Delay: The cumulative delay along the path.
  3. Reliability: The reliability of the path.
  4. Load: The current load on the path.
  5. MTU: The Maximum Transmission Unit of the path.

This cheatsheet provides a quick reference for EIGRP configuration, verification, and key concepts. It can help you with basic EIGRP configuration tasks and understanding the protocol’s features and operations.