Which statement about NAT is true?

Which statement about NAT is true?

• A. NAT translates public addresses to private addresses and always enables direct connections.
• B. NAT translates private addresses to a public address; can block direct connections; NAT traversal techniques (UPnP, STUN, TURN) help.
• C. NAT is the same as a firewall and does not affect peer-to-peer connections.
• D. NAT only affects UDP communications.

Answer: (B)

NAT translates private addresses to a public address and can block direct connections, so NAT traversal techniques like UPnP, STUN, and TURN are used to help peers communicate behind NAT. Think of NAT as a translator at the border of a private network. It lets many devices share one public IP by mapping each internal address and port to a public one. But that mapping also means unsolicited traffic from the outside often can’t find the right inside device, unless the NAT device has a mapped port or a relay is used. That’s why direct peer-to-peer connections between devices on different networks can fail without traversal methods. UPnP can automatically create port mappings, STUN helps determine the public address and NAT behavior to establish a path, and TURN can relay traffic when a direct path can’t be established.

NAT translates private addresses to a public address and can block direct connections, so NAT traversal techniques like UPnP, STUN, and TURN are used to help peers communicate behind NAT.

Think of NAT as a translator at the border of a private network. It lets many devices share one public IP by mapping each internal address and port to a public one. But that mapping also means unsolicited traffic from the outside often can’t find the right inside device, unless the NAT device has a mapped port or a relay is used. That’s why direct peer-to-peer connections between devices on different networks can fail without traversal methods. UPnP can automatically create port mappings, STUN helps determine the public address and NAT behavior to establish a path, and TURN can relay traffic when a direct path can’t be established.