Objective 5

Here we are going to perform unequal cost load balancing accross the 256kbps and 128kbps link via EIGRP.  This is done via the variance command which is set to 1 by default, which means it will only load balance with equal links (bandwidth speed).

To load balance we will use the variance 2 command, which means "I will load balance accross links that are twice as bad as my primary"

If we check the topology table we shall see the metric for each route;

BB-Router# show ip eigrp topology
IP-EIGRP Topology Table for AS(90)/ID(172.30.8.1)

P 10.1.2.0/24, 1 successors, FD is 10514432
         via 10.1.34.2 (10514432/28160), Serial0/1
         via 10.1.24.2 (20537600/281600), Serial0/0

The primary route has a metric of 10514432 (256kbps) and the fessiable sucessor has a metric of 20537600 (128kbps) which is rougly twice as bad;

10514432 x 2 = 21028864

So by using the variance command using a multiplier of 2 (as this will would encompass the 128kbps links metric) we can load balance


BB-Router(config)#router eigrp 90
BB-Router(config-router)#variance ?
  <1-128>  Metric variance multiplier
BB-Router(config-router)#variance 2

Lets check the routing table now;

BB-Router#show ip route

     172.30.0.0/16 is variably subnetted, 10 subnets, 2 masks
C       172.30.2.0/24 is directly connected, Loopback2
C       172.30.3.0/24 is directly connected, Loopback3
D       172.30.0.0/21 is a summary, 00:00:20, Null0
C       172.30.0.0/24 is directly connected, Loopback0
C       172.30.1.0/24 is directly connected, Loopback1
C       172.30.6.0/24 is directly connected, Loopback6
C       172.30.7.0/24 is directly connected, Loopback7
C       172.30.4.0/24 is directly connected, Loopback4
C       172.30.5.0/24 is directly connected, Loopback5
C       172.30.8.0/24 is directly connected, Loopback8
     10.0.0.0/8 is variably subnetted, 5 subnets, 3 masks
D       10.1.2.0/24 [90/10514432] via 10.1.34.2, 00:00:20, Serial0/1 
                    [90/20537600] via 10.1.24.2, 00:00:20, Serial0/0
C       10.1.24.2/32 is directly connected, Serial0/0
D       10.1.25.0/24 [90/10642432] via 10.1.34.2, 00:00:20, Serial0/1 <--- load balancing
                     [90/20640000] via 10.1.24.2, 00:00:20, Serial0/0           <--- load balancing


Now we can see we are load balancing over both links, EIGRP will intelligent load balance over the links, for every 2 packets send over the 256kbps link it will send 1 packet of the 128kbps .... AWESOME!