Here you will find how to setup PPTP VPN protocol on DD-WRT router. Setting up HeadVPN access under DD-WRT router is simple. The following instructions go step-by-step through the creation process of a PPTP VPN connection.
Connect to the router using either an Ethernet cable, or by joining the wireless network. Open a web browser, and load the following address: http://192.168.1.1
Go to Setup then select Basic Setup.

Under Connection Type select PPTP.

Under Use DHCP select Yes.

Under Gateway (PPTP Server) enter the IP address of the server you want to connect.
Under User Name enter your VPN username.
Under Password enter your VPN password.

Enable PPTP Encryption.

Disable STP

MTU change to Manual and set to 1460 as value.

Enter an IP address for the DD-WRT access point. Note, if this is the second router then you must set a different Local IP address then your main router.

Enable DHCP Server and uncheck all three checkboxes for ‘Use DNSMasq for DHCP’, ‘Use DNSMasq for DNS’ and ‘DHCP-Authoritative’.

Apply Settings

Click on Security then Firewall and set to Disabled SPI Firewall.

Click on Security then click on VPN Passthrough and enable PPTP Passthrough.

Apply Settings.

Click on Administration Tab scroll down and click on Reboot Router.

After the router will reboot it should connect to the VPN automatically. You can check the connection status by going to Status -> WAN tab. If Login Status say Connected then it’s OK, if not click to connect.
You are DONE! Now your DD-WRT router share your regular internet connection via VPN network.

Enjoy HeadVPN service!