What Ports To Open for L2TP VPN
Here are the ports and protocols:
There are several different ports listed when you Google this topic. In practice I have found that I only need to open UDP 500 and UDP 4500 in order for VPN to work.
- 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)
Also, Port 1701 is used by the L2TP Server, but connections should not be allowed inbound to it from outside. There is a special firewall rule to allow only IPSEC secured traffic inbound on this port.