linux - Which ports for IPSEC/LT2P? - Server Fault

MikroTik: L2TP/IPsec VPN Firewall Rules - Dec 17, 2017 VPN Pass-Through Setup | DrayTek 2. Go to NAT >> Open Ports, and open the required port to the IP address of the VPN server. The ports required for each protocol are: PPTP: TCP 1723 (the router will also forward GRE IP47 automatically) L2TP: UDP 1701 ; IPsec: UDP 500 and UDP 4500 if NAT-T is used (the router will also forward ESP IP50 automatically) 3. FortiClient open ports Remote IPsec VPN access: UDP/IKE 500, ESP (IP 50), NAT-T 4500: Remote SSL VPN access: TCP/443 (by default; this port can be customized) SSO Mobility Agent, FSSO: TCP/8001: Compliance and Security Fabric: TCP/8013 (by default; this port can be customized) FortiGuard What is IPSEC? - Internet Protocol Security Explained

Double & triple checked the port forwards, deleted & recreated the rules a few times to be sure; There are no other pre-existing L2RP/IPSec port forward rules or otherwise conflicting port forward rules (e.g.: another rule for ports 500, 1701 or 4500) There was an L2TP port triggering rule enabled, that I toggled on and off with no change

Aug 13, 2019

IPSEC has no ports. In IPv4 IPSEC, or to be more precise AH (authentication header) and ESP (encapsulation security payload), are two IP protocols just like TCP and UDP. In IPv6 IPSEC is part of the protocol are there are two extension headers one for authentication and one for encryption.

How to set up VPN server with port forwarding? | Official Apr 24, 2019 What Ports To Open for L2TP VPN | What Ports To Open for L2TP VPN Protocol: UDP, port 500 (for IKE, to manage encryption keys) Protocol: UDP, port 4500 (for IPSEC NAT-Traversal mode) Protocol: ESP, value 50 (for IPSEC) Protocol: AH, value 51 (for IPSEC) Ports in IPSec tunnel - Network Engineering Stack Exchange