all the neighbors that can reach the destination, and their associated metrics.
  • Router A then sends an update packet to router B.
  • Upon receiving the update packet, router B sends an acknowledgement packet to router A.
    • After routers A and B successfully receive the update packets from each other, they are ready to update their routing tables with the successor routes from the topology table.
    Content 2.2 EIGRP Components and Operation 2.2.7 EIGRP Metric EIGRP uses the same composite metric components as the legacy Cisco routing protocol, IGRP, including bandwidth, delay, reliability, load, and maximum transmission unit (MTU). The only difference between the IGRP and EIGRP composite metrics is that the EIGRP metric is multiplied by 256, because it uses 32 bits instead of 24 bits. Although the metric can be based on five criteria, EIGRP uses only two of these criteria by default: Three other criteria can be used, but are not recommended, because they typically result in frequent recalculation of the topology table:
    Content 2.2 EIGRP Components and Operation 2.2.8 EIGRP Metric Calculation EIGRP calculates the metric by adding together weighted values of different variables of the link to the network in question. EIGRP assigns K values to represent each metric. The K values are carried in EIGRP hello packets. The default constant weight values are K1 = K3 = 1, and K2 = K4 = K5 = 0. You can verify the K values by using the show ip protocols command. In EIGRP metric calculations, when K5 is 0 (the default), variables (bandwidth, bandwidth divided by load, and delay) are weighted with the constants K1, K2, and K3. The following is the formula used: If these K values are equal to their defaults, the formula becomes the following: If K5 is not equal to 0, the following additional operation is performed: Note
    Mismatched K values can cause a neighbor to be reset. (Only K1 and K3 are used, by default, in metric compilation.) These K values should be modified only after careful planning. Changing these values can prevent your network from converging and is generally not recommended. Figure displays the output of the show ip eigrp command. Notice the metric values assigned for the 172.16.102.1 network. Figure displays the output of the show interface command and the bandwidth and delay values. Note that the format of the delay and bandwidth values used for EIGRP metric calculations is different than those displayed by the show interface command. The EIGRP delay value is the sum of the delays in the path, in tens of microseconds multiplied by 256, while the show interface command displays delay in microseconds. Therefore, the metric value displayed by the command must be divided by 10 before it can be used in the metric calculation formula. The EIGRP bandwidth is calculated using the minimum bandwidth link along the path, in kilobits per second. The value 107 is divided by this value, and then the result is multiplied by 256. Interactive Media Activity Checkbox: EIGRP Metric Calculation

    Upon completion of this activity, the student will be able to identify the equation for calculating EIGRP and IGRP metrics.
    Web Links EIGRP Metric Calculation Example
    http://www.cisco.com/en/US/tech/tk365/technologi es
    _white_paper09186a0080094cb7.shtml#eigrpmetrics
    Content 2.2 EIGRP Components and Operation 2.2.9 EIGRP Metric Calculation Example Figure illustrates an example network in which router A has two paths to reach networks behind router D. The bandwidths (in kilobits per second) and the delays (in tens of microseconds) of the various links are also shown in the figure. The least bandwidth along the top path (A → B → C → D) is 64 kbps. The EIGRP bandwidth calculation for this path is as follows: The delay through the top path is as follows: Therefore, the EIGRP metric calculation for the top path is as follows: The least bandwidth along the lower path (A → X → Y → Z → D) is 256 kbps. The EIGRP bandwidth calculation for this path is as follows: The delay through the lower path is as follows: Therefore, the EIGRP metric calculation for the lower path is as follows: Router A therefore chooses the lower path, with a metric of 12,048,000, over the top path, with a metric of 41,536,000. Router A installs the lower path, with a next-hop router of X and a metric of 12,048,000, in the IP routing table. The bottleneck along the top path, the 64-kbps link, can explain why the router takes the lower path. This slow link means that the rate of transfer to router D would be at a maximum of 64 kbps. Along the lower path, the lowest speed is 256 kbps, making the throughput rate up to that speed. Therefore, the lower path represents a better choice to move large files quickly.
    Content 2.3 VLSM 2.3.1 Configuring Basic EIGRP Knowing the correct commands to configure EIGRP helps ensure a quicker migration with less troubleshooting. Perform the following steps to configure EIGRP for IP: Step 1 Enable EIGRP and define the autonomous system using the router eigrp autonomous-system-number command. The autonomous system number value must match on all routers within the autonomous system. Step 2 Indicate which networks are part of the EIGRP autonomous system using the network command. This command determines which interfaces of the router are participating in EIGRP and which networks the router advertises. Figure lists the parameters for the network command. Step 3 When using serial