Port 1701 · L2TP

Port 1701 is L2TP, UDP.

Layer 2 Tunneling Protocol — typically paired with IPSec. Used by Windows built-in VPN client.

Palo Alto

Create the service object for this port, then allow the App-ID on it. Restricting the rule to the port's service object keeps the rule working on a non-default port and stops the App-ID matching on other ports. Replace the placeholders with your own rule name and zones.

set service udp-1701 protocol udp port 1701

set rulebase security rules <rule-name> from <from-zone> to <to-zone> source any destination any application l2tp service udp-1701 action allow

Risk and exposure

Rated low risk. Even so, only expose this port to the networks and hosts that need it, and keep it patched.

Check it

• Linux ss -ulnp | grep :1701
• nmap nmap -sU -p 1701 <host>

Related ports

• 500 IKE / ISAKMP
• 4500 IPSec NAT Traversal
• 4501 GlobalProtect IPSec
• 1194 OpenVPN
• 1723 PPTP
• 1812 RADIUS Auth

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