Cisco IOS cheat sheet for EIGRP (Enhanced Interior Gateway Routing Protocol) — Cisco-proprietary distance-vector/diffusing-update routing protocol. Covers basic setup, timers, key-chain authentication, load balancing, and diagnostics.
Basic Configuration
EIGRP Setup
| Command | Description |
|---|---|
| router eigrp 1 | Enter EIGRP AS 1 context |
| no auto-summary | Enable classless mode, disable automatic summarization |
| network 192.168.1.0 0.0.0.255 | Advertise network to all EIGRP neighbors |
| passive-interface fa0/0 | Suppress hello packets on interface (toward end users) |
| eigrp stub [connected|receive-only|redistributed|static|summary] | Receive all routes but advertise only selected types |
| neighbor 192.168.2.0 | Manually define neighbor (NBMA / frame-relay) |
| no ip split-horizon eigrp 100 | Disable split-horizon on the interface |
Timers
Hello and Hold Timers
| Command | Description |
|---|---|
| ip hellow-interval eigrp 1 10 | Send hello packets every 10 seconds (per interface) |
| ip hold-timer eigrp 1 30 | Declare neighbor dead after 30 s without hello |
EIGRP hello/hold timers on two neighboring routers do not have to match, unlike OSPF.
Metric and Load Balancing
Metric Tuning and Load Balancing
| Command | Description |
|---|---|
| metric weights <TOS> <K1> <K2> <K3> <K4> <K5> | Change K-values (0–255 each; TOS must be 0) |
| metric maximum-hops <1-255> | Max hop count (default 100) |
| variance 2 | Unequal-cost load balancing: use feasible successors up to 2× cost of successor |
| maximum-paths 6 | Max equal-cost paths for load balancing |
| traffic-share balanced | Distribute traffic inversely proportional to metric |
| traffic-share min | Send all traffic via lowest-metric path only |
| ip summary-address eigrp 1 10.64.0.0/14 | Advertise summary route on the interface |
Diagnostics
show / debug
| Command | Description |
|---|---|
| show ip eigrp neighbors | Routers with active EIGRP adjacency |
| show ip eigrp interfaces | Interfaces participating in EIGRP |
| show ip eigrp topology [all-links] | EIGRP topology table (successor + feasible successors) |
| show ip eigrp interface detail fa0/0 | Timer values per interface |
| show ip eigrp traffic | EIGRP packet counters |
| show ip protocols | Dynamic routing protocol config (AS, networks, AD) |
| debug eigrp | Real-time EIGRP debug output (turn off with: undebug all) |
Key-Chain Authentication
Synchronize time on all routers (NTP) before configuring authentication.
Key Chain Definition
| Command | Description |
|---|---|
| key chain MYKEYS | Create key chain named MYKEYS |
| key 1 | Define key 1 in the chain |
| key-string cisco | Set key 1 value |
| accept-lifetime 18:00:00 may 21 2015 18:00:00 may 22 2015 | Window during which this key is accepted from neighbors |
| send-lifetime 18:00:00 may 21 2015 18:00:00 may 22 2015 | Window during which this key is sent to neighbors |
| key 2 | Key 2 — automatically takes over after key 1 expires |
| key-string cisco2 | Set key 2 value |
Apply Authentication to Interface
| Command | Description |
|---|---|
| ip authentication mode eigrp 1 md5 | Enable MD5 authentication for EIGRP instance 1 |
| ip authentication key-chain eigrp 1 MYKEYS | Specify key chain to use for authentication |
Cisco IOS Command Reference | EIGRP