In preparation of your CCNA exam, we want to make sure we cover the various concepts that we could see on your Cisco CCNA exam. So to assist you, below we will discuss the following CCNA concept; how to enable the Interior Gateway Routing Protocol. As you progress through your CCNA exam studies, I am sure with repetition you will find this topic becomes easier. So even though it may be a difficult concept and confusing at first, keep at it as no one said getting your Cisco certification would be easy!
Enabling Interior Gateway Routing Protocol
Interior Gateway Routing Protocol (IGRP) is a distance vector routing protocol with sophisticated metrics and improved scalability, allowing better routing in larger-sized networks. IGRP uses delay and bandwidth as routing metrics (reliability and load are optional). IGRP has a default maximum hop count of 100 hops. (RIP’s maximum is 15 hops.) This can be reconfigured to 255 hops. IGRP can load-balance across six nonequal paths, increasing the available bandwidth and providing route redundancy.
IGRP Metrics
IGRP achieves greater route selection accuracy than RIP with the use of a composite metric. The path that has the smallest metric value is the best route. IGRP’s metric includes the following components: bandwidth delay, reliability (based on keepalives), loading (bits per second), and maximum transmission unit (MTU). You can significantly affect performance by adjusting IGRP metric values.
Paths of Different Metrics
IGRP allows load balancing over unequal paths. If two unequal paths are used and one path is four times better than the other, the better path will be used four times as often. The variance command specifies the metric range allowed for load balancing across multiple paths. Here’s the procedure for configuring IGRP:
RouterA>enable
RouterA#config term
RouterA(config)#router igrp 100
RouterA(config-router)#network 170.8.0.0
RouterA(config-router)#variance 1
RouterA(config-router)#traffic share balanced
RouterA(config-router)#exit
RouterA(config)#exit
RouterA#show ip protocols
The syntax for the router IGRP command includes the AS number. All routers within an autonomous system must use the same system number.
The default value of variance is 1 (equal-cost load balancing).
The traffic share balanced command distributes traffic proportionally to the metrics’ ratios.
Use show ip protocols to verify the IGRP protocol configuration.
Use show ip route to display the contents of the IP routing tables.
Enabling IGRP Summary
We hope you found this Cisco certification article helpful. We pride ourselves on not only providing top notch Cisco CCNA exam information, but also providing you with the real world Cisco CCNA skills to advance in your networking career.

 IGRP has increased scalability and a more sophisticated routing metric than RIP. IGRP can load balance over unequal paths.
IGRP’s routing metric is a composite of bandwidth, delay, reliability, load, and MTU.
The debug ip igrp configuration commands display routing and transaction information for troubleshooting purposes.