EIGRP Metric Calculation Process

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EIGRP uses a classic metric calculation formula

      *It use total Delay throughout the destination

      *least bandwidth in between source to destination to find the metric

      *Routers always use the receiving end link properties to do the metric and calculation

Configuration of R1, R2, R3 & R4

      *R1(config)#router eigrp 10

      *R1(config-router)#network 12.0.0.0

      *R1(config-router)#network 14.0.0.0

      *R1(config-router)#exit

      *R2(config-if)#router eigrp 10

      *R2(config-router)#network 12.0.0.0

      *R2(config-router)#network 23.0.0.0

      *R2(config-router)#exit

      *R3(config)#router eigrp 10

      *R3(config-router)#network 23.0.0.0

      *R3(config-router)#network 34.0.0.0

      *R3(config-router)#network 3.0.0.0

      *R3(config-router)#exit

      *R4(config)#router eigrp 10

      *R4(config-router)#network 14.0.0.0

      *R4(config-router)#network 34.0.0.0

      *R4(config-router)#exit

So now we have 2 path to reach Router R3 loopback address from Router R1 one is via Router R2 and one is via Router R4

We will check both metric calculation and will check the RT also to cross check Let’s start from R1-R2-R3-Loopback

      *R1 F0/0 Bandwidth is 100000 & Delay is 100

      *R2 G3/0 Bandwidth is 1000000 & Delay is 10

      *R3 Loopback Bandwidth is 8000000 & Delay is 5000

So now we need to find least bandwidth and Total Delay

      1. Least bandwidth is 100000

      2. Total Delay is 5110

After this calculation answer will be 156416

Now let’s do for another Path R1-R4-R3-Loopback

      *R1 F1/0 Bandwidth is 100000 & Delay is 100
      *R4 F0/0 Bandwidth is 100000 & Delay is 100
      *R3 Loopback Bandwidth is 8000000 & Delay is 5000

So now we need to find least bandwidth and Total Delay

      1. Least bandwidth is 100000
      2. Total Delay is 5200

After the calculation answer is 158720

So now we have both Metric values via R2 is 156416 & via R4 is 158720

Now best path will be via lowest metric value and that is via R2.

Metric Weight & Metric Components

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So we have two types of stuff in Metric one we have is metric weights and one we have is metric components

Metric Weights	Metric Components
K1 is 1	Bandwidth
K2 is 0	Load
K3 is 1	Delay
K4 is 0	Reliability
K5 is 0	MTU

*By default we use K1 and K3 and both belongs to metric component Bandwidth and Delay
*K values range can be from 0 to 255
*When we increase K values so corresponding Metric will be Multiplied by same number

*If R1 is using K1 as 2 and K3 as 2 so R2 should have same K values otherwise routers will give error of K-Values Mismtach

*But we can tweak Metric Components on any router and need to be same on both routers
*When we tweak Metric components that router use new metric calculation with new metric components
*We can change 100Mb link to 10Mb just to change metric calculation or for path manipulation

               Check out our Complete EIGRP Video on Youtube