router eigrp [as-number]
Enters EIGRP router configuration mode for a specific autonomous system number, allowing you to configure EIGRP routing protocol parameters.
router eigrp [as-number]When to Use This Command
- Enable EIGRP on a router and advertise directly connected networks to neighbors.
- Configure EIGRP router ID, timers, or stub routing for a specific AS.
- Set EIGRP metric weights or redistribute routes from other routing protocols.
- Modify EIGRP hello and hold timers to tune convergence.
Command Examples
Basic EIGRP Configuration with Network Statements
router eigrp 100
network 192.168.1.0
network 10.0.0.0Router(config)# router eigrp 100 Router(config-router)# network 192.168.1.0 Router(config-router)# network 10.0.0.0 Router(config-router)#
The command 'router eigrp 100' enters EIGRP configuration mode for AS 100. The 'network' commands advertise the specified networks to EIGRP neighbors. No output is shown unless there is an error.
EIGRP with Router ID and Stub Configuration
router eigrp 200
eigrp router-id 1.1.1.1
eigrp stub connected summaryRouter(config)# router eigrp 200 Router(config-router)# eigrp router-id 1.1.1.1 Router(config-router)# eigrp stub connected summary %DUAL-5-NBRCHANGE: EIGRP-IPv4 200: Neighbor 10.0.0.2 (GigabitEthernet0/0) is down: stub configuration change Router(config-router)#
The 'eigrp router-id' sets the router ID manually. The 'eigrp stub' command configures the router as a stub, advertising only connected and summary routes. The log message indicates a neighbor adjacency reset due to the stub configuration change.
Understanding the Output
The 'router eigrp [as-number]' command itself does not produce output; it changes the CLI prompt to 'config-router'. Subsequent configuration commands may generate log messages (e.g., neighbor changes) or error messages if syntax is incorrect. In a real network, after configuring EIGRP, you would use 'show ip eigrp neighbors' to verify neighbor adjacencies and 'show ip eigrp topology' to view the topology table. Key fields in neighbor output include 'Hold' (time before neighbor is declared dead), 'Uptime' (how long adjacency has been up), and 'Q Count' (queue count, should be 0). A high Q count or frequent neighbor flapping indicates issues. In topology output, 'P' (passive) means route is stable, 'A' (active) means DUAL is recalculating—active routes should be transient. Good values: neighbors in 'Init' or 'Up' state, routes passive. Bad values: neighbors stuck in 'Init' or 'Down', routes stuck in active (SIA).
CCNA Exam Tips
CCNA exam tip 1: EIGRP uses autonomous system numbers (1-65535); both routers must use the same AS number to form adjacency.
CCNA exam tip 2: The 'network' command is classful by default; use 'network x.x.x.x 0.0.0.255' for wildcard mask to be precise.
CCNA exam tip 3: EIGRP stub routing is a common exam topic—remember 'eigrp stub' limits queries and prevents transit traffic.
CCNA exam tip 4: The 'eigrp router-id' command is used to set a stable router ID; if not configured, the highest loopback IP is used.
Common Mistakes
Mistake 1: Forgetting to use the same AS number on all routers in the EIGRP domain, preventing neighbor adjacency.
Mistake 2: Using a classful network statement without a wildcard mask, causing incorrect interface activation.
Mistake 3: Configuring 'eigrp stub' without specifying 'connected' or 'summary', which may not advertise all desired routes.
Related Commands
show ip eigrp neighbors
Displays the neighbor table for EIGRP, showing all directly connected EIGRP routers and their status, used to verify EIGRP adjacencies and troubleshoot neighbor relationships.
show ip eigrp topology
Displays the EIGRP topology table, showing all learned routes and their feasible successors, used to verify EIGRP convergence and path selection.
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