NAT vs PAT
NAT translates private IP addresses to public ones; PAT is a form of NAT that lets many devices share one public IP by tracking them with port numbers. PAT (also called NAT overload) is what your home router does.
The core difference
| NAT (static/dynamic) | PAT (overload) | |
|---|---|---|
| Maps | One private IP to one public IP | Many private IPs to one public IP |
| Uses port numbers | No | Yes — to tell sessions apart |
| Public IPs needed | One per host | Just one for everyone |
| Where you see it | Servers needing a fixed public IP | Every home router |
How PAT shares one IP
Plain NAT maps one private IP to one public IP — fine for a server, but you would need a public IP per device, and there are not enough. PAT maps every internal device to the same public IP but a different port number, then uses that port to send each reply back to the right device. One public IP can serve hundreds of hosts (see NAT explained).
10.0.0.11:51000 to 203.0.113.5:51000 10.0.0.12:49000 to 203.0.113.5:49000 (same public IP, different ports)
When to use which
PAT (overload) for general internet access — the default for homes and offices. Static NAT when a server needs a consistent public IP. Configure both in the NAT config guide.
Frequently asked questions
What is the difference between NAT and PAT?
NAT maps private IPs to public IPs, typically one-to-one. PAT (Port Address Translation, or NAT overload) maps many private IPs to a single public IP using different port numbers to keep sessions separate.
Is PAT a type of NAT?
Yes — PAT is a form of dynamic NAT, also called NAT overload. It is the most common type because it lets many devices share one public IP address.
Why does PAT use port numbers?
Because many devices share one public IP, the router needs a way to tell their sessions apart. It assigns each a unique source port and uses it to route replies back to the correct device.
What does my home router use, NAT or PAT?
PAT (NAT overload). All your devices share the single public IP your ISP assigns, distinguished by port numbers.
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