UDP 1701
Synopsis
- UDP port 1701 is used by the Layer 2 Tunneling Protocol (L2TP) control channel.
- Microsoft Windows Server Remote Access/ RRAS and the built‑in Windows VPN client use UDP 1701 for L2TP/IPsec remote‑access VPNs.
- Apple macOS and iOS VPN clients, and Android’s built‑in L2TP/IPsec client, connect on UDP 1701.
- On Linux, xl2tpd and accel-ppp provide L2TP servers listening on UDP 1701; SoftEther VPN Server and MikroTik RouterOS also use this port.
- Network gear from Cisco (ASA/IOS routers), Juniper (SRX), Ubiquiti EdgeRouter/UniFi, Fortinet FortiGate, and DrayTek supports L2TP on UDP 1701 for remote‑access and ISP LNS roles.
- Many ISPs transport subscriber PPP sessions over L2TP on UDP 1701 between LACs and LNSs; for example, BT Wholesale in the UK hands off broadband sessions to ISPs via L2TP.
- Security: exposed L2TP/UDP 1701 services are commonly probed for credential brute‑forcing and have been abused for UDP reflection DDoS when they respond to unauthenticated control messages.
Observed activity
Last 30 days
Detailed chart