Linux Desktop Hacks

Connect to a Microsoft PPTP VPN #68

Chapter 8, Desktop Programs

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HACK

If the module loads without error, everything is well; otherwise, you need to

obtain or build the ppp_mppe kernel module. If you are using a stock distri-

bution kernel, this could be as simple as installing the required package. If a

package isn’t available, you need to build a custom kernel. The required ker-

nel option (using menuconfig) is Network Device Support

➝ PPP (point-to-

point protocol) Support

➝ PPP MPPE Compression (encryption).

You also need to use Version 2.4.2 or above of the ppp package. Now you

need to edit the /etc/ppp/chap-secrets file to contain the following:

## OUTBOUND CONNECTIONS

username "*" password

Again, you should replace both username and password with the values your

network administrator gives you. If you are running a firewall at your end

(you should be!), you need to configure the firewall to allow all packets out

on TCP port 1723 to the VPN server. This is used to negotiate the connec-

tion and to pass link control traffic. The only other change that is required is

to allow all GRE protocol packets (protocol number 47) between the client

system and the VPN server. You should do this for both inbound and out-

bound traffic.

Starting the VPN

Now everything should be ready to go. To make a connection, log in as root

and run the following command:

foo@bar:~# pptp-command start office

Using interface ...