EIGRP Metric Calculation and Formulas

Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary routing that they developed to address the limitations of other distance vector routing protocols such as RIP by being able to implement unequal-cost load balancing. EIGRP metric can support networks even if they are 255 hops away and has quick convergence features.

One feature of EIGRP is that it uses various factors to calculate the metric for its path. EIGRP metric values, by default, utilize bandwidth value and delay value but also consider interface load and reliability. Below is the formula for EIGRP classic metric calculation:

EIGRP Metric


What are EIGRP K-Values?

The metric calculation in EIGRP considers the K-values used to calculate the best route. The value can be between 0-255 and independently set, with reference to what is considered for the cost calculation for each route. If an attribute is not considered, the K-value for that should be equal to zero, but if it is considered, the K-value should be equal to one.

As stated, the maximum K-value for EIGRP metrics is 255, so the ability to manipulate what route metric is defined during the path calculation. For example, if you want the Bandwidth to be a priority over Delay, you can configure the K-value of K1 to be higher than K3.

EIGRP offers flexibility in deciding which route to prioritize by setting the K-values of the preferred attribute in the routing domain. It is important to remember that EIGRP neighbors must have matching K-values.


EIGRP Classic Metric Formula with Default K-values

When considering the default K-values in calculating the EIGRP metric calculation formula of the route, K1 and K3 should always be 1, and K2, K4, and K5 are zero. The EIGRP formula is derived from the IGRP metric formula, then multiplied by 256 to change the calculation from 24 to 32 bits. Bandwidth is the slowest link referenced to a 10 Gbps link (107). The link speed is from the configured Bandwidth on the interface, and Delay values are the quantity of the total measure of path delay in microseconds.

EIGRP IGRP Metric Formula


By calculating the above equation considering all the default K-values, we will come up with the EIGRP Classic Metric formula.

Classic EIGRP Metric Formula


The table below shows the default EIGRP Interface Metrics that we can use for the Classic Metric formula:

Interface Type Link Speed (Kbps) Delay Metric
Serial 6420,000 μs40,512,000
T1 154420,000 μs2,170,031
Ethernet 10,0001000 μs281,600
FastEthernet 100,000100 μs28,160
GigabitEthernet 1,000,00010 μs2816
10 GigabitEthernet 10,000,00010 μs512


Using the Classic EIGRP Metric formula, let us compute the EIGRP metric of the network below passing through R1> R3>R4 to the destination network.

EIGRP Metric Example


The link speed is 1 Gigabit, so it is 1,000,000 Kbps for the minimum Bandwidth and the total Delay is 30μs. Therefore, the metric would be 3328.

EIGRP Metric Computation


The route metrics can be checked using the ‘show ip eigrp topology’ command. The network and subnet mask are added at the end of the command to view the detailed EIGRP information of the route. The show command below shows the details of the EIGRP route from R1 to the network. You can see that the metric calculated, 3328, is the same as the metric in the output below:


R1#sh ip eigrp topology
EIGRP-IPv4 Topology Entry for AS(1)/ID( for
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3328
  Descriptor Blocks: (GigabitEthernet1), from, Send flag is 0x0
      Composite metric is (3328/3072), route is Internal
      Vector metric:
        Minimum bandwidth is 1000000 Kbit
        Total delay is 30 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 2
        Originating router is


Wide Metrics

EIGRP specifications originally measured Delay to be 10 microseconds and the Bandwidth in kbps which is not scalable with interfaces with higher speeds. With this issue, EIGRP wide metrics formula has a second set that addresses the scalability limitations with higher-speed interfaces by adding a K-value in the EIGRP metric calculations, which is K6 that measures the jitter, energy, and other attributes in the future.

EIGRP Wide Metrics


EIGRP wide metrics scale by 65,536 to support 655 Tbps (65,536 × 107) interface speed without any scalability issue. The scaled EIGRP wide metrics formula takes scalability and latency, which is the total delay in picoseconds, into account.

EIGRP Wide Metrics Scaled


EIGRP Metric Backward Compatibility

The EIGRP wide metrics were developed with the ability to be backward compatible. As long as K1 through K5 are the same and K6 is not provided or is equal to zero, the classic metric and wide metrics can establish adjacency between routers.

Moreover, EIGRP can detect when the peering between two routers uses classic metric, thus unscaling a metric from the formula.

EIGRP Backward Compatibility


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