What is NAT traversal and why is it needed for peer-to-peer or VPN connections?

• A. NAT traversal translates private IPs to public IPs on a gateway for outbound web traffic.
• B. NAT traversal helps peers behind NAT establish connections by exchanging public addresses or relaying traffic through a TURN server; methods include STUN and TURN.
• C. NAT traversal is unnecessary because NAT always allows direct connections.
• D. NAT traversal encrypts translations to secure traffic.

Answer: (B)

NAT traversal is about enabling devices behind a NAT to establish connections with peers or VPN endpoints on the public Internet. Because NAT maps private addresses to a public one, unsolicited inbound connections are blocked unless a path or mapping is created. NAT traversal uses techniques like STUN to discover the device’s public address and test connectivity, and TURN to relay traffic through a publicly reachable server when a direct path can’t be established. This makes P2P and VPN connections possible across NAT boundaries, since peers can either open a direct path or have their traffic relayed. The best choice describes exactly this collaboration of exchanging public addresses or relaying via a TURN server, with STUN and TURN as representative methods. The other options miss the core idea: NAT traversal isn’t just about translating private IPs for outbound traffic, it’s about enabling inbound connectivity; it isn’t always unnecessary because direct connections aren’t guaranteed behind NAT; and it isn’t primarily about encrypting translations.