Vpn-server configuration based on pptpd service in ubuntu.

1) Install pptpd in any way you like.

2) enable forwarding packets between interfaces:

$ sudo sysctl -w net.ipv4.ip_forward=1

Check configuring:

$ cat /proc/sys/net/ipv4/ip_forward 
1 

3) The file /etc/pptpd.conf should look like this:

option /etc/ppp/pptpd-options
logwtmp
localip 10.0.0.1
remoteip 10.0.0.100-200

localip — address of virtual network interface ppp0 (that appears after connecting the client to the server)

remoteip — the range of addresses for customers

4) The file /etc/ppp/chap-secrets should look like this:

box1 pptpd 11 "*"
box2 pptpd 22 "10.0.0.101"

box1 and box2 — are the user's names (login)

11 and 22 — are user's passwords (password)

"*" - assigning any address from the address range

"10.0.0.101" — assigning a specific address

5) The file /etc/ppp/pptpd-options should look like this:

name pptpd
refuse-pap
refuse-chap
require-mschap-v2
refuse-mschap
require-mppe-128
ms-dns 8.8.8.8
ms-dns 8.8.4.4
mtu 1400
mru 1400
nodefaultroute
proxyarp
lock
nologfd
noipx
nobsdcomp
novj
novjccomp

6) Restart the server:

service pptpd restart

checking that pptpd - server is working:

$ sudo netstat -alpn | grep :1723 
tcp        0      0 0.0.0.0:1723            0.0.0.0:*               LISTEN      28401/pptpd    

but at that time the output of the command ifconfig will not show the presence of interface ppp0

On client side in ubuntu we create the connection using:
«Change connection» -> VPN

Settings for the new vpn-connection:
Gateway — 192.168.1.10 (address of eth0 interface)
Name of user — box1
Password — 11
Authentification only mschapv2
Encryption MPPE (any available)
Comression all disable

After user connection there will be the interface on the server:

$ ifconfig
ppp0      Link encap:Протокол PPP (Point-to-Point Protocol)  
          inet addr:10.0.0.1  P-t-P:10.0.0.100  Mask:255.255.255.255 
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1396  Metric:1 
          RX packets:18 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:3 
          RX bytes:784 (784.0 B)  TX bytes:84 (84.0 B) 

На клиенте появиться соединение:

$ ifconfig
ppp1      Link encap:Протокол PPP (Point-to-Point Protocol)  
          inet addr:10.0.0.100  P-t-P:10.0.0.1  Mask:255.255.255.255 
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1400  Metric:1 
          RX packets:6 errors:0 dropped:0 overruns:0 frame:0 
          TX packets:43 errors:0 dropped:0 overruns:0 carrier:0 
          collisions:0 txqueuelen:3 
          RX bytes:84 (84.0 B)  TX bytes:3781 (3.7 KB)