CCNA EIGRP: Passive Interfaces

Bundle lab · $29.99

Build and verify EIGRP on a small routed topology while marking the user-facing LAN interface as passive. You will advertise the LAN into EIGRP without forming an adjacency on that segment, preventing rogue neighbors and reducing control-plane noise. Focus on deterministic EIGRP configuration, wildcard-based network inclusion, and verification using show commands.

Learning objectives

• Enable EIGRP (AS 100) with classless behavior using 'no auto-summary'.
• Advertise only the intended subnets via precise EIGRP wildcard statements.
• Apply 'passive-interface' on the LAN so no EIGRP neighbors form on user segments.
• Keep the router-to-router transit active so adjacency forms normally.
• Verify with 'show ip protocols', 'show ip eigrp interfaces', 'show ip eigrp neighbors', and 'show ip route eigrp'.
• Explain why passive interfaces harden the edge and reduce unnecessary hellos.

Troubleshooting focus

• AS number mismatch across routers prevents EIGRP adjacency.
• Missing or incorrect 'network' wildcard on the transit prevents neighbor formation.
• Marking the transit as passive stops EIGRP hellos and breaks adjacency.
• Omitting the LAN network statement stops its advertisement even if the interface is passive.
• Shut or mis-addressed interfaces prevent control-plane formation regardless of routing config.