EIGRP Metric Calculator

EIGRP Metric: Bandwidth & Delay

The Enhanced Interior Gateway Routing Protocol is an advanced distance-vector IGP. It stayed Cisco-proprietary until 2013, when it appeared as an informational standard in RFC 7868. The composite metric can draw on five K-values (K1 bandwidth, K2 load, K3 delay, K4/K5 reliability), but Cisco ships with K1=K3=1 and the rest at 0. That trims the formula down to metric = (K1·BW + K3·Delay) · 256 for classic EIGRP, where BW = 10⁷ / minimum bandwidth (kbps) along the path and Delay is the sum of interface delays in tens of microseconds.

What makes EIGRP converge fast is the Diffusing Update Algorithm (DUAL). It works out a loop-free Feasible Successor (FS) right next to the active Successor (S) and keeps both in the topology table. If the successor drops, DUAL hands traffic to the feasible successor in milliseconds, no full recomputation needed. Only when there's no FS available does the router go Active and start querying neighbors. Wide-metric EIGRP, added for 64-bit metrics, stretches the formula so multi-Gbps interfaces don't overflow it.

Applications

You'll find EIGRP all over enterprise campuses running Cisco backbones. The draw is sub-second convergence, unequal-cost load balancing through the variance command, and a lighter CPU footprint than OSPF's SPF runs. It also turns up in SD-WAN underlays and in DMVPN hub-and-spoke setups, where the topology shifts often.

FAQ

Why multiply by 256? Old IGRP carried a 24-bit metric. EIGRP bumps it to 32 bits, and to 64 bits in wide-metric mode, by multiplying the IGRP value by 256. That keeps things backward compatible.

What is a Feasible Successor? It's a backup next-hop whose reported distance comes in below the current feasible distance. That condition is what guarantees a loop-free fallback without DUAL having to go active.

Is EIGRP still proprietary? Not since 2013, when Cisco put it out as an informational RFC. In practice, though, non-Cisco implementations are still limited, so multi-vendor networks tend to reach for OSPF or IS-IS instead.