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IntermediatePublished 2026-07-02

CCNA NAT4: PAT Overload onto a Pool

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Implement Port Address Translation (PAT) using a one-address NAT pool so multiple inside hosts share a single public IP. Reuse the same 5-node topology and addressing as the prior lab; convert the pool to a single address and enable overload. Verify simultaneous connectivity from two inside hosts, observe translations and counters, and contrast with prior pool-exhaustion behavior.

Track
Est. time
45 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Configure PAT (overload) using a NAT pool with a single global address
  • Mark inside and outside NAT interfaces correctly so translations occur across the edge
  • Build a source-selection ACL for NAT and validate its hit counters
  • Verify concurrent inside sessions share one public IP via distinct port mappings
  • Interpret NAT translation and statistics outputs to confirm overload behavior

Troubleshooting focus

  • No translations appear: verify inside/outside roles and that traffic crosses the edge
  • ACL 1 does not match: confirm source network and wildcard mask
  • Return traffic fails: ensure the edge router has a default route to the ISP
  • Only one host works intermittently: confirm overload is configured on the pool

Topology

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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.
  • 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.
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