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BeginnerPublished 2026-07-03

EIGRP Fundamentals: First Adjacency & Route Exchange

Free preview — the first lab of EIGRP Routing

Bring up EIGRP in AS 100 between two routers over a /30 transit and advertise a single LAN. Verify the first adjacency forms and that R2 learns R1's LAN via EIGRP. Includes realistic end hosts on a shared LAN for path testing.

Track
Est. time
35 minutes
Difficulty
Beginner
Topics

Learning objectives

  • Enable EIGRP with a consistent AS number and default K-values across routers
  • Use network statements with correct wildcards to activate EIGRP on the intended interfaces
  • Disable auto-summary for classless behavior
  • Verify EIGRP adjacency formation and route exchange with core IOS show commands
  • Validate end-to-end reachability from a host across the routed transit

Troubleshooting focus

  • If neighbors do not form, confirm both sides use the same EIGRP AS and that the shared transit is matched by a network statement on both routers.
  • Confirm IP addressing, masks, and interface status on the transit: both ends must be in 10.0.12.0/30 and up/up.
  • Check show ip protocols to ensure auto-summary is disabled and the correct networks are included.
  • On R2, if 192.168.1.0/24 is missing from the routing table, confirm R1 advertises that LAN and that adjacency is up.
  • From the host, if you can ping the default gateway but not R2, suspect missing EIGRP advertisement or neighbor down.

Topology

Lab topology diagram

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