Last Updated on July 31, 2021 by Admin
You are the network administrator for a large software organization. You designed the LAN in the organization’s main building for connecting the internal LAN to a WAN as shown below:
You have configured EIGRP with the variance parameter set to 3 on all the routers to enable unequal load balancing from the 172.16.1.0 network to the WAN. The delay configured on each of the routers is shown in the LAN diagram, and the K values are set as follows:
K1 = 0
K2 = 0
K3 = 1
K4 = 0
K5 = 0
Which of the following paths are entered into the routing tables as a result of the unequal load balancing configured on the routers? (Choose all that apply.)
The only path is entered in the routing table as a result of the unequal load balancing configured on the routers:RA-RB-RE-RI-RKIn EIGRP networks, bandwidth and delay are the default factors for calculating the metric/cost for a given route. Additional factors such as load and reliability can be considered in the computation of the EIGRP metric, as given in the following formula:Metric = [K1 * bandwidth + (K2 * bandwidth) / (256 – load) + K3 * delay] * [K5 / (reliability + K4)]In this case, only the K3 value has a non-zero value. This implies that only delay is taken into consideration to calculate the metric of the shortest path from 172.16.1.0 network to the WAN. The path with the lowest metric, which is delay in this scenario, is the shortest path, and is therefore entered automatically in the routing table. The total delay and the corresponding metric for the three best paths are given as follows:
In the given table, the path RA-RB-RE-RI-RK has the lowest metric of 14080. This is the shortest path, so it would be entered in the routing table even if variance were not enabled. In this scenario variance is set to 3, which enables unequal load balancing among those paths that have a metric less than three times the least metric for the given route. Three times the least metric in this scenario is 42240 (14080 x 3). This implies that paths between the 172.16.1.0 network and the WAN having a metric less than 42240 participate in the load balancing. On metric values alone, those paths would appear in the routing tables. However, to be eligible to be a feasible successor the reported distance of the path must be less than the feasible distance (current best path). None of the paths, with the exception of RA-RB-RE-RI-RK meet that requirement.
The path RA-RB-RD-RH-RK is not entered in the routing table as a result of the unequal load balancing. The scaled EIGRP delay for this path is 43520 (170 x 256), which is more than three times the least metric available from the 172.16.1.0 network to the WAN (42240). In addition, the reported distance for this path is more than the feasible distance. Therefore, the path RA-RB-RD-RH-RK is not used for balancing the load from the 172.16.1.0 network to the WAN and does not appear in the routing tables.
Layer 3 Technologies
Configure and verify EIGRP load balancing