CentOs 5.5 PPTP VPN installation and configuration

Source: Internet
Author: User
Tags centos iptables

VPN (Virtual private network) is an extension of a private network that sends data between a local computer and a remote computer by sharing an Internet or public network connection to simulate point-to-point private connections.

It has good confidentiality and immunity from interference, allowing both sides to be free and secure point-to-point connection.

There are two common VPN services under Linux, one is PPTP and the other is OpenVPN. The former is simpler, but only standalone servers and Xen VPS can be built, the latter without any restrictions. The former built VPN, do not need a special VPN client, directly under Windows to create a VPN dial-up connection, and the latter need to install a client to dial

Network Experiment Environment:

Server version: CentOs 5.5

VPN server: eth0= eth0:1=

Intranet IP Address:

Extranet IP Address:

Check if the server has the necessary support.

If the check results do not support this, PPTP cannot be installed. Execution Instructions:

#modprobe ppp-compress-18 && Echo OK

After this execution, the show "OK" indicates the pass. But then you need to do another check and enter the instructions:


If the instruction shows the result to the following text, it means:

Cat:/dev/net/tun:file Descriptor in

All of the above two passes to install PPTP. Otherwise you can only consider OpenVPN, or ask your service provider to solve this problem.

The Cent OS 5.5 kernel version is above 2.6.15, so the following check can be ignored:

Check if PPP supports MPPE

Check to see if PPP supports MPPE with the following command:

#strings '/USR/SBIN/PPPD ' |grep-i MPPE | WC--lines

If the above command output is "0", it is not supported, the output is "30" or a larger number is supported, MPPE (Microsoft Point to Point Encryption, Microsoft Point-to-Point encryption).

Second, the installation of PPP and iptables.

By default, the complete CentOS is provided with these two components, but a compact version of the system may not. We enter the following command to confirm that if it is not installed, some of the system will not do any action:

#yum install-y PPP Iptables

Third, install PPTP.

This software is not in the Yum source, we need to manually download. Let's switch to the TMP directory first:


Then execute the following command to download the PPTP installation package:

#wget http://acelnmp.googlecode.com/files/pptpd-1.3.4-1.rhel5.1.i386.rpm (32-bit system use)

#wget http://acelnmp.googlecode.com/files/pptpd-1.3.4-1.rhel5.1.x86_64.rpm (64-bit system use)

CentOS more than 6 system please download: wget http://poptop.sourceforge.net/yum/stable/packages/pptpd-1.3.4-2.el6.x86_64.rpm (64 for system use)

If your CentOS is 32-bit, execute the 32-bit instruction, and if it is a 64-bit CentOS, execute the 64-bit instruction. Be careful not to make a mistake, the error will be wrong after the client connection is not 619 or 800, and prompted pptpd-logwtmp.so can not find.

Next, you install PPTP, which is also divided into 32-bit and 64-bit systems:

#rpm-IVH pptpd-1.3.4-1.rhel5.1.i386.rpm (32-bit system use)

#rpm-IVH pptpd-1.3.4-1.rhel5.1.x86_64.rpm (64-bit system use)

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