If the router has two types of routes, for the same network, the router chooses Administrative Distance to choose the best one. But in some cases, there will be two paths found by the same protocol, to the destination network. Here the routing protocol will use routing metric value to find the best path.

Example: RIP (Routing Information Protocol) uses hop count as the metric.

Following are some of the factors to choose a best path to destination.

Metric	Routing Protocols	Description
Bandwidth	IP EIGRP, IP IGRP	The bandwidth of the links in Kbps (T1=1,554)
Cost	IP OSPF	Measurement in the inverse of the bandwidth of the links
Delay	IP EIGRP, IP IGRP	Time it takes to reach the destination
Hop count	IP RIP	How many routers away from the destination
Load	IP EIGRP, IP IGRP	The path with the least utilization
Reliability	IP EIGRP, IP IGRP	The path with the least amount of errors or downtime

If a router found multiple paths with the same administrative distance and metric to a destination, load balancing can occur. Cisco IOS Software has a limit of six equal-cost routes on the routing table, but some protocols set their own limitations. For example, EIGRP allows up to four equal-cost routes.

Related Topics...

• What is Dynamic Routing and different types of Dynamic Routing

• Introduction to Distance Vector Routing Protocols

• Introduction to Routing Information Protocol (RIP)

• How to configure Routing Information Protocol (RIP)

• Introduction to Interior Gateway Routing Protocol (IGRP)

• How to configure Interior Gateway Routing Protocol (IGRP)

• Introduction to Link State Routing Protocols

• Introduction to Open Shortest Path First (OSPF) Protocol

• How to configure Open Shortest Path First (OSPF)

• Introduction to Hybrid Routing Protocols

• Introduction to Enhanced Interior Gateway Routing Protocol (EIGRP)

• How to configure Enhanced Interior Gateway Routing Protocol (EIGRP)