[How To] Enable VPN on Linux by PPTP - The Tech Tales: Chronicles of my tech journey

PPTP is an wonderful utility to enable VPN on a Linux box. Its secure and compatible with Windows network. I first heard about PPTP from (this wonderful guy called) Nikolaj. I have learnt how to set it up from him.
I am detailing the steps here:

1> Install PPTP

yum install pptp

2> vi /etc/ppp/options.pptp

###############################################################################

# $Id: options.pptp,v 1.2 2005/08/20 13:16:38 quozl Exp $

# Sample PPTP PPP options file /etc/ppp/options.pptp

# Options used by PPP when a connection is made by a PPTP client.

# This file can be referred to by an /etc/ppp/peers file for the tunnel.

# Changes are effective on the next connection. See "man pppd".

# You are expected to change this file to suit your system. As

# packaged, it requires PPP 2.4.2 or later from http://ppp.samba.org/

# and the kernel MPPE module available from the CVS repository also on

# http://ppp.samba.org/, which is packaged for DKMS as kernel_ppp_mppe.

###############################################################################

# Lock the port

lock

# Authentication

# We don't need the tunnel server to authenticate itself

noauth

persist

debug

# We won't do EAP, CHAP, or MSCHAP, but we will accept MSCHAP-V2

refuse-eap

refuse-chap

refuse-mschap

# Compression

# Turn off compression protocols we know won't be used

nobsdcomp

nodeflate

# Encryption

# (There have been multiple versions of PPP with encryption support,

# choose with of the following sections you will use. Note that MPPE

# requires the use of MSCHAP-V2 during authentication)

# http://ppp.samba.org/ the PPP project version of PPP by Paul Mackarras

# ppp-2.4.2 or later with MPPE only, kernel module ppp_mppe.o

# {{{

# Require MPPE 128-bit encryption

#require-mppe-128

# }}}

# http://polbox.com/h/hs001/ fork from PPP project by Jan Dubiec

# ppp-2.4.2 or later with MPPE and MPPC, kernel module ppp_mppe_mppc.o

# {{{

# Require MPPE 128-bit encryption

#mppe required,stateless

# }}}

lcp-echo-failure 36

lcp-echo-interval 5

lcp-max-failure 0

3> vi /etc/ppp/chap-secrets

# Secrets for authentication using CHAP

# client server secret IP addresses

VPNUserName PPTP VPNPassword *

4> Create a file called /etc/ppp/peers/my-company-vpn

#pty "pptp my-company.com --nolaunchpppd"

name VPNUserName

remotename PPTP

require-mppe-128

file /etc/ppp/options.pptp

ipparam my-company-vpn

5> Then on the prompt:

pptp my-company.com call my-company-vpn

6> After 10/15 seconds, on the prompt:

route -n

You should see something like:

Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface

192.168.1.162 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0

87.61.21.102 192.168.1.1 255.255.255.255 UGH 0 0 0 eth0

192.168.1.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0

If you see ppp0, it means you have successfully connected to the VPN.

7> Add required routes

route add -host 192.168.1.30 gw 192.168.1.162

Where 192.168.1.30 is my internal company IP.

8> After that, to resolve the domains by names

vi /etc/resolv.conf

#to use when connected to the VPN my-company.com

domain my-office.my-company.com

#this, is the most important line: courtesy: Nikolaj

search my-office.my-company.com

#nameserver 192.168.1.1

nameserver 192.168.1.4

nameserver 192.168.1.5