Which port is used by STUN in NAT traversal?

Which port is used by STUN in NAT traversal?

• A. 88
• B. 3389
• C. 3478
• D. 5900

Answer: (C)

In NAT traversal, STUN is used to discover how a device behind a NAT appears to the outside world, including its mapped public address and port. The standard port STUN uses for sending and receiving binding requests is 3478, typically over UDP (with some implementations supporting TCP or TLS on alternate ports). This port is registered specifically for STUN, which is why it’s the expected default in most setups. The other ports shown correspond to unrelated services (for example, 3389 for RDP, 5900 for VNC, 88 for Kerberos) and aren’t used by STUN.

In NAT traversal, STUN is used to discover how a device behind a NAT appears to the outside world, including its mapped public address and port. The standard port STUN uses for sending and receiving binding requests is 3478, typically over UDP (with some implementations supporting TCP or TLS on alternate ports). This port is registered specifically for STUN, which is why it’s the expected default in most setups. The other ports shown correspond to unrelated services (for example, 3389 for RDP, 5900 for VNC, 88 for Kerberos) and aren’t used by STUN.