Install open VPN , PPTP and L2tp Client network manager ubuntu

apt-get install network-manager-openvpn
sudo apt-add-repository ppa:seriy-
pr/network-manager-l2tp
sudo apt-get update
sudo apt-get install network-manager-l2tp-gnome

http://forum.openvz.org/index.php?t=msg&goto=49760&
I've found that xt_tcpudp module seem to be included in the kernel packages of Debian 6, but not of CentOS 6. I don't know if it can be installed with some additional package (yum).


http://forum.openvz.org/index.php?t=msg&goto=8117
Hi,

iptables "MASQUERADE" isn't virtualized,
only listed iptables modules can be used in VE context:
(see man-page of vzctl)

iptable_filter,iptable_mangle, ipt_limit, ipt_multiport,
ipt_tos, ipt_TOS,ipt_REJECT, ipt_TCPMSS, ipt_tcpmss,
ipt_ttl, ipt_LOG, ipt_length, ip_conntrack, ip_conntrack_ftp,
ip_conntrack_irc, ipt_conntrack, ipt_state, ipt_helper,
iptable_nat, ip_nat_ftp, ip_nat_irc, ipt_REDIRECT xt_mac. 

iptables -t nat -A POSTROUTING -j SNAT --to-source <venet's IP>

 http://sourceforge.net/p/ipsec-tools/bugs/70/

modprobe af_key 

http://superuser.com/questions/570612/how-do-i-get-l2tp-to-successfully-install-on-centos-5-9
http://lowendtalk.com/discussion/11171/implement-of-l2tp-in-an-openvz-container 


ifconfig.me
execute command without saving in history .
space and command  

how to configure pptp and freeradius

pptp authentication using freeradius you can following tutorials.

For freeradius setup : http://safesrv.net/install-and-setup-freeradius-on-centos-5/
For pptpd setup      : http://safesrv.net/setup-pptp-and-freeradius-on-centos-5/

After radius server installation test radius server locally and remote server. If response is positive then you are done with radius server. Else add nas table to radius server if is it is already not included or not already configured.

Try not to jump on another server deployment util you are not completely deployed previous one.

If you are unable to communicate between user , VPN server and freeRADIUS server then check IPTABLES and port forwarding. And also check that in VPN server configuration ,  radius server ip is defined.
Also confirm that in freeRADIUS configuaration ,   VPN server ip is listed in clients.
After successfull setup of these two servers following are possible issues you may face.

Possible issue :
Issue 1 : Carefully read tutorial and do configuration of right files. Because some directories contains file names with little difference for example options.pptpd and options-pptpd.

Issue 2 : User requires some authentications like pap , chap , mschap etc. User sends authentication requests to VPN server and VPN sever forward this request to freeRADIUS server to authenticate user.

Authentication will only be successfull if user's required authentications matches with /etc/ppp/pptpd-options configuration. In /etc/ppp/options-pptpd  authentications are written like this require-pap refuse-pap etc.

Still having problem please read this freeradius official tutorial http://wiki.freeradius.org/guide/PopTop-HOWTO   .

pptp Unknown attribute 47. Modem hang up

You are setting up PPTP Using freeRADIUS server.

freeRADIUS server is ready to process requests. And PPTP is accepting connections.

Windows clients are working fine and browsing successfully.

Ubuntu PPTP clients connect to server but in less than 10 sec they disconnect.

Server logs:
Server log is showing modem hangup.
Unknown attribute 47.
Unknown attribute 48.

Solution:
This is client side error. The server is working fine. There is no need to check server.

We found the solution in the following link.
http://ubuntuforums.org/showthread.php?t=1479655&p=9279383#post9279383

This is maximum transmission unit error on client side. (MTU , the size of largest protocol data unit)

To solve this issue only change MTU of interface through which you are connected to internet.
Enter following command in terminal.

sudo ifconfig eth0 mtu 1400

Change eth0 to interface from which you are connected to internet. MTU value of 1400 at client side. PPTP is connected and not disconneting any more. No modem hang up error on client side.