How to allow Mac to connect to PPTP VPN using Raspberry Pi 3?

Question

PPTP support in macOS Sierra is dropped, check this for information, there are no free alternatives.

I know I can easily configure my Raspberry Pi to connect to VPN server using PPTP. Is there any way where I can tweak my Raspberry Pi (which is already connected to PPTP VPN), to allow my MacBook to connect to it (using Wi-Fi, Ethernet), so that I can access my server with the MacBook?

I am assuming there should be way where traffic from my MacBook can be redirected to Raspberry Pi, which behaves as a VPN server which is already connected to my server?

I may be completely wrong in my assumption :(

Note: I have posted this question in ASK different site, but unfortunately they have declared it as a "duplicate" which is not in any possible sense :(

Answer 1

You need to configure your Pi to route between the VPN interface and its local network interface and then configure the Mac to use the Pi as a gateway to the VPN.

You'll need to know address of the network you're connecting to when you connect your VPN; if it's not obvious from the configuration you can run ip route on the Pi before and after connecting and see what new routes were added. I'll use 10.128.0.0/16 (netmask 255.255.0.0) as an example.

On your Pi, once the VPN is connected, you need only enable packet forwarding with

echo 1 >/proc/sys/net/ipv4/ip_forward`.

To configure your Mac to use your Pi as the gateway to the VPN network you use (with 192.168.10.11 as the example Pi address):

route add 10.128.0.0 192.168.10.11 255.255.0.0

(The parameters are network address, gateway address and netmask of the network address.)

If you have difficulties, the easiest way to debug is to use tcpdump on your Pi. You can have it running twice in different windows with different -i options to look at the VPN interface and the LAN interface at the same time and see what's arriving and leaving on each.