Lab 55 - EIGRP Unequal Cost Load Balancing

Prerequisites: CCNP level skills.

Topology

Pic. 1 - Topology Diagram.

Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task1
R1 has currently two equal cost paths towards R3's Loopback interfaces. Ensure that R1 uses all paths available using unequal cost load balancing.

Lab Solution

Task1

R1 has currently two equal cost paths towards R3's Loopback interfaces. Ensure that R1 uses all paths available using unequal cost load balancing.

Notice!
The task does not stipulate how load balancing should work.

First, check in R1's routing table towards the subnets in question.

Pic. 2 - R1's Routing Table.

Currently, R2 is not listed as a gateway towards the subnets in question. EIGRP Topology will reveal the AD R2 advertises.

Pic. 3 - R1's EIGRP Topology Table.

In order for R2 (10.1.124.2) to be used as the gateway with unequal cost LB, it must be a feasible successor. Now, It is not since its AD equals the best FD. Using default K-values the formula to calculate the metric can be simplified to the following:

Metric = (Bandwidth + Delay) * 256

where:
Bandwidth = 10 to the 7th power / the_slowest_link_in_the_path (in Kbps)
Delay = sum_of_all_delays_in_the_path / 10

Based on the output in the pic. 3 I must modify either the bandwidth or delay to make R2 a feasible successor. The latter is easier.

R1 Configuration:

!

interface Serial0/0
 ip address 10.1.123.1 255.255.255.0
 encapsulation frame-relay
 delay 3000
 serial restart-delay 0
 frame-relay map ip 10.1.123.2 103
 frame-relay map ip 10.1.123.3 103 broadcast
 no frame-relay inverse-arp

!

interface Serial0/1
 ip address 10.1.13.1 255.255.255.0
 delay 3000
 serial restart-delay 0

!

Note!
Clear ip eigrp neighbor command is required to refresh the topology table.

R2 becomes the successor with R1's both links as two feasible successors.

Pic. 4 - R1's Topology Table (output truncated).

FD = 2300416
AD = 2553856

Variance 2 will do.

R1 Configuration:

!

router eigrp 1
 variance 2
 network 10.1.13.1 0.0.0.0
 network 10.1.123.1 0.0.0.0
 network 10.1.124.1 0.0.0.0
 network 172.16.101.1 0.0.0.0
 no auto-summary

!

Verification:

Pic. 5 - R1's Routing Table.