NAT / PAT Simulator

Routing

Overview

NAT rewrites address tuples; PAT additionally maps ports so multiple inside sessions share one outside address. Return packets must match active mappings. NAT does not inherently authenticate a user or replace firewall policy. Logging inside/outside tuples aids troubleshooting.

Protocol stages

1Inside tuple
2Translation entry
3Outside tuple
4Return lookup

Interactive exercise

Knowledge check

Two clients use source port 5000 to the same public service through one PAT address. How are simultaneous sessions distinguished?

Assign distinct translated source portsGive both exactly the same full tupleDelete the destination IP

Educational model — not real hardware, traffic or official certification.