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BeginnerPublished 2026-07-04

CDP Neighbor Discovery and Edge Suppression

Free preview — the first lab of Network Discovery & Monitoring

Enable Cisco Discovery Protocol (CDP) on R1 to map directly-connected Cisco neighbors while suppressing CDP advertisements on the untrusted management-edge interface. Routers are directly cabled for true CDP adjacency and also share a common management LAN via SW1 alongside an Alpine MGMT host.

Track
Est. time
35 minutes
Difficulty
Beginner
Topics

Learning objectives

  • Explain why CDP only discovers directly connected Cisco devices
  • Enable CDP globally and verify neighbor formation on point-to-point links
  • Disable CDP advertisements on untrusted host-facing interfaces
  • Use show cdp neighbors and show cdp neighbors detail to inventory adjacencies
  • Differentiate discovery on the management LAN vs. router-to-router links

Troubleshooting focus

  • No neighbors appear when CDP is disabled globally
  • An interface shows no neighbors if it is administratively down or cabled incorrectly
  • Seeing the switch as a neighbor on the management LAN but not other routers is expected (CDP is link-local)
  • Host-facing ports should not advertise CDP; verify per-interface disablement

Topology

Lab topology diagram

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How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
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