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BeginnerPublished 2026-06-28

IPv4 Addressing Fundamentals: Interfaces, Gateways & Reachability

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Beginner CCNA lab focusing on IPv4 addressing and basic Layer 3 verification on a small branch network. You will assign IP addresses to router interfaces, confirm end-host default gateways, and verify connected reachability using host-based pings. You will also learn to read 'show ip interface brief' and 'show ip route' to confirm operational state before any routing beyond directly-connected networks is configured.

Track
Est. time
50 minutes
Difficulty
Beginner
Topics

Learning objectives

  • Apply IPv4 addressing to router interfaces in a multi-subnet small-branch topology
  • Confirm and reason about end-host default gateways in a routed LAN
  • Verify link and host reachability using ping from the end hosts
  • Interpret 'show ip interface brief' and 'show ip route' to validate interface state and connected routes
  • Troubleshoot common IP addressing and cabling errors that prevent basic connectivity

Troubleshooting focus

  • Fix mismatched IP and mask on router interfaces and hosts
  • Resolve down/down or err-disabled switch ports and shut router interfaces
  • Correct wrong or missing default gateway on hosts
  • Use 'show ip route' and 'show interfaces status' to localize L1/L2 vs L3 faults

Topology

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Grade your work

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.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
  • Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.

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