May 03, 2018

IP Protocol Scan (-sO) | Nmap Network Scanning Protocol scan works in a similar fashion to UDP scan. Instead of iterating through the port number field of a UDP packet, it sends IP packet headers and iterates through the eight-bit IP protocol field. The headers are usually empty, containing no data and not even the proper header for the claimed protocol. Getting a PPTP VPN to Work through a Netgear Firewall In addition to port 1723, IP protocol 47 must also be allowed - note that this is *not* a TCP or UDP port - it's an IP protocol called GRE (TCP and UDP are also IP protocols, with their own associated numbers).

Digi Connect® WAN Application Helper

Jan 05, 2017 RFC 8086 - GRE-in-UDP Encapsulation

[ScreenOS] What ports are used for a Virtual Private

Apr 19, 2018 mikrotik allow pptp | Syed Jahanzaib Personal Blog to PPTP uses the GRE protocol, You have to allow ip PROTOCOL 47 (GRE), not TCP port. TCP port 1723 is the control connection, while the actual tunnel is GRE (protocol 47). Example: /ip firewall filter add action=accept chain=input disabled=no dst-port=1723 protocol=tcp add action=accept chain=input disabled=no protocol=gre Understanding Firewall Port Configuration Among Aruba Devices