Big companies use things like VPNs to give you access to some servers, and thats cool when you have a nice graphical interface to do that.
But!! when it comes to connect a GNU/Linux machine to a VPN PPTP with only a command line available, you can take some good time till discover how to do that.
So, I'm going to explain in a very short way how to establish your connection to the VPN, and we are going to name it my-vpn.
1. Install the software that you will need
sudo apt-get install pptp-linux
2. Create a configuration file for the peer connection
sudo vi /etc/ppp/peers/my-vpn
Then put the configuration parameters
Replace "vpn-server.your-client.com" with the real url of the VPN server and "taller" with the VPN user name.
# Url of the VPN server.
pty "pptp vpn-server.your-client.com --nolaunchpppd"
# VPN user name.
# Adopt defaults from the pptp-linux package.
3. Configure the connection credentials.
sudo vi /etc/ppp/chap-secrets
Put the credentials
Replace taller with your VPN user name and PASSWORD with the password.
# Secrets for authentication using CHAP
# client server secret IP addresses
taller my-vpn 123456 *
4. Let's connect our selves.
sudo pon my-vpn nodetach &
Now if everything goes as expected, check if a new lan interface named ppp0 Point-to-Point Protocol.
5. But! that's not it!! must route some of the traffic to the VPN.
Let's create a file to always have this route up and running.
sudo vi /etc/ppp/ip-up.d/my-vpn
Put the routing rule. Take a look at the IP range, maybe in your VPN is different.
route add -net 192.168.0.0/24 dev ppp0
Make it executable, and run it!
sudo chmod +x /etc/ppp/ip-up.d/my-vpn
6. Resolving domains.
We could config a some DNS to resolve the domains inside the VPN, but I prefer doing manually, so the traffic is all controlled. See this post for how to do the resolving thing.
sudo vi /etc/hosts
...and put this for example:
6. DONE !!
If you want to unplug the VPN connection, just do this:
sudo poff my-vpn
There are some other ways to do it, but this one, worked for me!! and now I can connect to my client LDAP through his VPN.