If it is make sure port 1723 and protocol 47 are allowed. Many consumer grade routers have PPTP passthrough disabled by default. On Linksys brand routers there is a section in configuration called 'Filters' that you have to change.
GRE - Generic Routing Encapsulation a Cisco VPN for Apr 26, 2016 GRE Protocol 47 Forwarding : eero GRE Protocol 47 Forwarding Has anyone figured out how to forward the GRE(General Routing Encapsulation, Protocol 47) protocol through the eeros? I am trying to get my home network vpn server working, but the mobile app does not show any vpn passthrough options and the port forwarding only shows TCP & UDP. cannot pass PPTP via protocol 47 (GRE) through WRT We are trying to make VPN connections from a branch office through a WRT54GS router. The connections fail, as protocol 47 (GRE) is apparently not
Jan 31, 2020
GRE - Generic Routing Encapsulation a Cisco VPN for Apr 26, 2016
Generic Routing Encapsulation on the Cisco CMTS - Cisco
Jul 25, 2015 Configuring PPTP Through PAT to a Microsoft PPTP Server Oct 19, 2006 Windows Ports, Protocols, and System Services - TechNet Port Protocol Application protocol System service name n/a: GRE: GRE (IP protocol 47) Routing and Remote Access: n/a: ESP: IPsec ESP (IP protocol 50) Routing and Remote Access: n/a: AH: IPsec AH (IP protocol 51) Routing and Remote Access: 7: TCP: Echo: Simple TCP/IP Services: 7: UDP: Echo: Simple TCP/IP Services: 9: TCP: Discard: Simple TCP/IP Generic Routing Encapsulation on the Cisco CMTS - Cisco