Monday, January 30, 2017

EIGRP Overview

EIGRP Overview

EIGRP (Relevant) Tables
  • Neighbor Table - Directly connected routers -  show ip eigrp neighbors 
  • Topology Table - Successor / Feasible Successor Routes -  show ip eigrp topology {all-links}
  • Routing Table   - The best routes from the topology table -  show ip route {eigrp}

Adjacency Terminology
  • Hello - Forms Relationships 
  • Update - Sends updates 
  • Query - Asks about Routes 
  • Reply - Responce to Query 
  • Ack - Acknowledges the update, query, and reply messages.
  • SIA (Stuck-in-Active) - This is bad... Waiting for Query to see if any router knows the network route.
    • Here is a crappy GIF I made to make things more clear.

Routing Terminology
  • Advertised Distance (AD) - The distance the neighbor has listed for a network.
  • Feasible Distance (FD) - The AD + the cost of the interface.
  • Successor - The route that has the lowest FD.
  • Feasible Successor - The routes with a lower FD than the Successor.
    • Note: To be considered a Feasible Successor, the AD must be less than the FD of the successor. This is called the Feasibility Condition.
  • Active Route - The route is down and you are actively trying to find a route for that network.
  • Passive Route - There is no activity on the route to the network.


  1. We are at the exact same point in our CCNP ROUTE studies, it seems! Will be following this blog closely, and hopefully making a few post of my own.

    1. Hey, I just passed my CCNP Route portion and I am on to TSHOOT. How is your studying?