When it comes to its entirety, the EIGRP metrics is a true beast.
Metric=256∗((K1∗BW)+(K2∗BW256−Load)+(K3∗Delay)(K5Reliability+K4))𝑀𝑒𝑡𝑟𝑖𝑐=256∗((𝐾1∗𝐵𝑊)+(𝐾2∗𝐵𝑊256−𝐿𝑜𝑎𝑑)+(𝐾3∗𝐷𝑒𝑙𝑎𝑦)(𝐾5𝑅𝑒𝑙𝑖𝑎𝑏𝑖𝑙𝑖𝑡𝑦+𝐾4))
The default K values are K1𝐾1 and K3=1𝐾3=1 while K2𝐾2, K4𝐾4, and K5𝐾5 = 0._
The equation presented above can be simplified to the following by using the default K values:
((107min−bandwidth)+SumOfDelays)∗256
Use the router configuration command metric weights to change the K values that are set by default.
|
K Value |
Component
|
Description |
|
K1 |
Bandwidth |
Lowest Route Bandwidth |
|
K2 |
Load |
highest packet rate-based load on the route |
|
K3 |
Delay |
Route’s cumulative interface latency |
|
K4 |
Reliability |
On the basis of keep alive, the routes with the worst reliability |
|
K5 |
MTU |
Path with the smallest MTU |
Bandwidth (K1)
The bandwidth command is where EIGRP initially gets the bandwidth it uses to calculate its metrics. It checks the interface’s default bandwidth if this method of bandwidth specification is not present. Never forget that adjusting an interface’s bandwidth value has no effect on the interface’s bandwidth or its policing. The only time it’s used is to affect routing protocols that factor bandwidth into their metrics. The metric calculation uses kilobits per second as its bandwidth.
Load (K2)
EIGRP will use the highest Txload number if K2 (Load) is turned on. The Load is shown on a range from 1 to 255, with 1 meaning the interface is empty and 255 meaning it is fully used.
Delay (K3)
A packet’s delay is proportional to the time it takes for it to traverse the interface. Interface type determines Cisco’s default delays. As an example, the default delay for FastEthernet is 100 microseconds. A range of 167,772,140 microseconds is available for delay configuration. The delay is entered in tens of microseconds, although it is shown in microseconds using the show interface command.
A router’s total latency is the sum of its own interface latency and the latency it receives from its neighbors.
Reliability (K4)
Reliability is determined by comparing all frames that were successfully received to all frames that were received. At a reliability rate of 100 per cent, all of the frames that we received were valid. The scale ranges from 0 to 255, with 255 representing the highest possible level of reliability.
MTU (K5)
In actuality, MTU in EIGRP is only used when the maximum-pathways command’s value is exceeded by equal cost paths to the same destination. In this case, pathways with a higher MTU will be chosen above ones with a lower MTU.
Putting Everything Together
Going back to the equation above:-.
