LOAD BALANCING WITH EIGRP

Load Balancing with EIGRP
By default EIGRP can load balance up to four equal-cost links. But did you know that you can configure EIGRP to load balance across up to six equal/ unequal-cost links to a remote network?

Router(config)#router eigrp 100 Creates routing process 100
Router(config-router)#network 10.0.0.0 Specifies which network to advertise in EIGRP
Router(config-router)#variance n Instructs the router to include routes with a metric less than or equal to n times the minimum metric route for that destination, where n is the number specified by the variance command , If a path is not a feasible successor, it is not used in load balancing.

For the route to be a feasible successor, its advertised distance must be less than the feasible distance of the successor route. You need to remember that even though both routes to network are in the topology table, only the successor route (the one with the lowest metrics) will be copied and placed into the routing table. EIGRP will load balance across both links automatically when they are of equal variance (equal cost), but EIGRP can also load balance across unequal cost links if you use the variance command. Changing a variance value enables EIGRP to install multiple, loop-free routes with unequal cost in a local routing table.

Bandwidth Use
NOTE: By default, EIGRP is set to use only up to 50 percent of the bandwidth of an interface to exchange routing information. Values greater than 100 percent can be configured. This configuration option might prove useful if the bandwidth is set artificially low for other reasons, such as manipulation of the routing metric or to accommodate an oversubscribed multipoint Frame Relay configuration.
NOTE: The ip bandwidth-percent command relies on the value set by the bandwidth command.

Bandwidth Authentication
Router(config)#interface serial 0/0 Enters interface configuration mode.
Router(config-if)#bandwidth 256 Sets the bandwidth to 256 kilobits to allow EIGRP to make a better metric calculation.
Router(config-if)#ip bandwidth-percent eigrp 50 100 Configures the percentage of bandwidth that may be used by EIGRP on an interface.
50 is the EIGRP autonomous system number. 100 is the percentage value.
100% * 256 = 256 kbps.