Port Address Translation (PAT), also called NAT Overload, lets many devices share a single public IP.
The concept:
- PAT modifies both IP addresses and port numbers
- Each connection gets a unique source port
- IP + port combination creates a unique identifier
Scale:
- One public IP theoretically supports ports
- In practice, - concurrent connections
- Reserved ports and timeouts reduce capacity
Example:
- Device A: 192.168.1.100:54321 becomes 203.0.113.5:40001
- Device B: 192.168.1.101:54321 becomes 203.0.113.5:40002
Both share 203.0.113.5 using different ports.