Saturday, 1 February 2020

Unequal Metric Load Balancing


As we have changed the metric on R4 s0/1 we doing primary and backup path scenario but is that fine??
Because we are wasting the directly connected s0/1 link. So we are decided to do load balance but without changing the metric. In Eigrp there is a unique feature Unequal metric load balancing.
So now let do it on R4.

R4#sh ip eigrp topology
P 150.5.5.0/24, 1 successors, FD is 2300416
        via 155.1.14.1 (2300416/156160), Serial0/0.41
        via 155.1.114.1 (2300450/156194), Serial0/1


R4 having both the path in topology but in routing table s0/0.41 is stored because of the lowest metric. Now we want R4 should do load balance. We have another link s0/1 having a metric greater than successor (2300450 > 2300416)

To do unequal metric load balance first we should find the variance value. Variance is the multiplier which make the feasible successor to use for packet forwarding.

Variance value =  Fd value of successor * multiplier(Any integer) >  FD value of others
                            = 2300416 * 2 > 2300450
Hence the variance is 2.
Configure this variance value in R4 and R4 will do the unequal load balance.

R4#sh run
 ip authentication mode eigrp 100 md5
 ip authentication key-chain eigrp 100 CISCO
router eigrp 100
 variance 2
 offset-list 1 in 34 Serial0/1
 network 150.4.0.0
 network 155.1.0.0
 no auto-summary
R4#sh ip route 150.5.5.0
Routing entry for 150.5.5.0/24
  Known via "eigrp 100", distance 90, metric 2300416, type internal
  Redistributing via eigrp 100
  Last update from 155.1.114.1 on Serial0/1, 00:03:45 ago
  Routing Descriptor Blocks:
    155.1.114.1, from 155.1.114.1, 00:03:45 ago, via Serial0/1
      Route metric is 2300450, traffic share count is 1
      Total delay is 25101 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2
  * 155.1.14.1, from 155.1.14.1, 00:03:45 ago, via Serial0/0.41
      Route metric is 2300416, traffic share count is 1
      Total delay is 25100 microseconds, minimum bandwidth is 1544 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 2

R4#traceroute 150.5.5.5
Type escape sequence to abort.
Tracing the route to 150.5.5.5
  1 155.1.114.1 60 msec
    155.1.14.1 84 msec
    155.1.114.1 4 msec
  2 155.1.156.5 32 msec *  48 msec
See the share count  and we are using both the link.
This means we formed the unequal load balancing.

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