What does NAT stand for?
NAT stands for Network Address Translation. Rewrites IP addresses in packet headers as traffic crosses a router, so many hosts with private (RFC 1918) addresses share one public address. It conserves IPv4 space and hides internal addressing, but it is not a security control on its own.
NAT rewrites IP addresses as packets cross a router or firewall. Its main use is to let many devices with private addresses share public ones. In its most common form, port address translation, a whole network goes out through a single public address and the device tells the connections apart by port number. NAT also hides the internal addressing from outside, though it is not a security control in itself.
NAT in practice: an example
Three laptops at 192.168.1.10, .11 and .12 browse the web through one public address. The router replaces each private source address with the public one and a different source port, and records the mapping. Replies come back to those ports and are translated back to the right laptop.
What NAT is confused with
NAT vs PAT: what is the difference?
PAT, also called NAT overload, is the many-to-one form of NAT that uses port numbers. Static NAT maps one private address to one public address. What PAT stands for
NAT vs firewall: what is the difference?
NAT changes addresses. A firewall decides which traffic is allowed. Home routers do both, which is why the two are often mixed up.
Which exams cover NAT?
NAT is on the official CompTIA acronym list for one of the four exams covered here.
- Network+ N10-009: 1.0 (Networking Concepts); 2.0 (Network Implementation).
Each number is a CompTIA exam objective and the name in brackets is its domain. The exam puts the term in a scenario; it does not ask you to recite the expansion.
Check yourself: two practice questions
Written by CertSprint for this page. They are not taken from any exam.
1. Fifty office PCs with private addresses share one public IP address. Which technique makes this possible?
- Port address translation
- Static NAT one-to-one
- VLAN trunking
- Link aggregation
Show the answer
A. Port address translation. PAT maps many inside addresses to one outside address by using different source ports.
2. An internal web server must be reachable from the internet at a fixed public address. Which type of NAT is used?
- Dynamic PAT
- Static NAT
- No NAT is possible
- DHCP relay
Show the answer
B. Static NAT. A static, one-to-one mapping gives the server a permanent public address that outside clients can target.
Sources: RFC 3022: Traditional IP Network Address Translator (Traditional NAT); NIST glossary: network address translation. The acronym and its expansion come from CompTIA's official acronym lists, linked from each exam glossary above. The explanation, example and questions are CertSprint's own, checked against these sources on 11 November 2026.