EIGRP Wide Metrics

In the previous lesson, you saw how EIGRP calculates the classic metric from the minimum bandwidth and the total delay.
That formula works well until the links become very fast.

Classic EIGRP was originally designed when high-speed interfaces were limited to 1 Gbps.

At that time, the metric formula scaled correctly for available link speeds.
However, modern networks now operate with 10 Gbps, 20 Gbps, 40 Gbps, and even 100 Gbps interfaces.

This is where the limitation appears.

A 10 Gbps Link vs a 20 Gbps Link

In this topology, one path uses a 10 Gbps link and another uses a 20 Gbps link.

Figure 1 – Classic EIGRP metric where 10G and 20G links produce the same cost

Even though 20 Gbps is twice as fast, the calculated metric is identical.
From EIGRP's perspective, both paths have the same cost.

The Bandwidth Term

The reason lies in how the bandwidth term is calculated in the classic formula:

Figure 2 – Classic EIGRP Bandwidth Term Calculation

The key limitation is that this value cannot go below 1.
Once the result reaches 1, it is treated as the minimum possible value.

The Bandwidth Term per Link Speed

Table 1 - Classic EIGRP Metric Saturation at 10 Gbps