Lab ips-05 - NAT Overload (PAT)

NAT overload - usually called PAT (Port Address Translation) - shares a SINGLE outside IP across many inside hosts by tracking the source port. Each internal connection gets a unique source port from the perspective of the outside; the router maintains the port-to-host mapping in its translation table. The vast majority of "NAT" in production is actually PAT. This lab configures PAT on R2 sharing Et0/1's IP across all inside hosts.

What you will learn

• PAT configuration with the overload keyword
• How PAT maps multiple inside hosts to one outside IP using source ports
• The translation table format with port columns
• Why PAT is the dominant NAT pattern in 2026

What this lab does NOT cover

• PAT with a pool (overload + pool combined)
• Inside source vs outside source PAT (rare)

Topology