How to Setup Windows 10 Firewall for L2TP/IPSec
Please check the port forwarding and firewall settings on your Synology NAS and router to make sure the TCP port 1723 is open. PPTP VPN service is built-in on some routers, the port 1723 might be occupied. To ensure VPN Server works properly, you might need to disable the built-in PPTP VPN service through the router's management interface to PPTP VPN on Ubuquiti EdgeRouter - LeerSpace Jul 15, 2015 Port Forwarding Setup for VPN Server – Firewalla If you lucky enough to have a UPnP enabled router or a NAT-PMP enabled router (Apple), Firewalla VPN should just work. In case it doesn't work, you will need to do a manual port forwarding. Basically, you need to map your router's public UDP port 1194 to Firewalla box port 1194.
Ports used for VPN Protocols – IPVanish
PFSENSE 2.3 PPTP VPN passthru workaround | Amixa Blog Jun 21, 2016 Point-to-Point Tunneling Protocol - Wikipedia
Check 4: Is your router running VPN. Some router may come with a default VPN server. If you want to use Firewalla VPN, please turn off your router VPN. Otherwise, the two VPN's will compete for 1194 port. Check 5: If Firewalla is in DHCP mode, is your overlay network configured to be the same subnet as primary network?
Mikrotik PPTP VPN Server Firewall Configuration - YouTube Jun 07, 2014 How to Setup Windows 10 Firewall for L2TP/IPSec