Which port number is used by the L2TP VPN protocol?

Which port number is used by the L2TP VPN protocol?

• A. 1701
• B. 443
• C. 80
• D. 1723

Answer: (A)

L2TP uses UDP port 1701. This protocol, Layer 2 Tunneling Protocol, is designed to carry PPP frames to establish a VPN tunnel and is typically implemented over UDP on that port. When L2TP is used with IPsec for security, IPsec handles encryption and negotiation via its own ports (IKE/ISAKMP on 500 and NAT-T on 4500, with ESP for payload), but the tunneling control still originates on UDP 1701. The other ports listed map to different services: 443 is HTTPS, 80 is HTTP, and 1723 is used by PPTP (which uses TCP, not UDP, for its control channel). So the port associated with L2TP is 1701.

L2TP uses UDP port 1701. This protocol, Layer 2 Tunneling Protocol, is designed to carry PPP frames to establish a VPN tunnel and is typically implemented over UDP on that port. When L2TP is used with IPsec for security, IPsec handles encryption and negotiation via its own ports (IKE/ISAKMP on 500 and NAT-T on 4500, with ESP for payload), but the tunneling control still originates on UDP 1701. The other ports listed map to different services: 443 is HTTPS, 80 is HTTP, and 1723 is used by PPTP (which uses TCP, not UDP, for its control channel). So the port associated with L2TP is 1701.