ситуация
SoftEther VPN у нас пока на Windows Server
необходимо подключить SoftEther VPN Linux Client

далее почти все просто.
забираем линукс клиента с оф.сайта softether.org, ставим.
и запускаем

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ./vpnclient
SoftEther VPN Client service program
Copyright © SoftEther VPN Project. All Rights Reserved.

vpnclient command usage:
 vpnclient start  - Start the SoftEther VPN Client service.
 vpnclient stop   - Stop the SoftEther VPN Client service if the service has been already started.


root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient#

далее настроим клиента.

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ./vpncmd
vpncmd command - SoftEther VPN Command Line Management Utility
SoftEther VPN Command Line Management Utility (vpncmd command)
Version 4.19 Build 9578   (English)
Compiled 2015/09/15 15:08:35 by yagi at pc25
Copyright © SoftEther VPN Project. All Rights Reserved.

By using vpncmd program, the following can be achieved.

1. Management of VPN Server or VPN Bridge
2. Management of VPN Client
3. Use of VPN Tools (certificate creation and Network Traffic Speed Test Tool)

Select 1, 2 or 3: 2

Specify the host name or IP address of the computer that the destination VPN Client is operating on.
If nothing is input and Enter is pressed, connection will be made to localhost (this computer).
Hostname of IP Address of Destination:

Access has been denied. Possibly the password is incorrect, or perhaps you are connecting by an incorrect admin mode. You can try inputting the password again. To cancel, press Ctrl+D.
Password: ******

Connected to VPN Client "localhost".

VPN Client>

VPN Client>AccountCreate
AccountCreate command - Create New VPN Connection Setting
Name of VPN Connection Setting: vpn-start

Destination VPN Server Host Name and Port Number: 192.168.20.10:5555

Destination Virtual Hub Name: DEFAULT

Connecting User Name: proxy

Used Virtual Network Adapter Name: tunvpn

The command completed successfully.

VPN Client>



VPN Client>AccountPasswordSet
AccountPasswordSet command - Set User Authentication Type of VPN Connection Setting to Password Authentication
Name of VPN Connection Setting: vpn-start

Please enter the password. To cancel press the Ctrl+D key.

Password: ******
Confirm input: ******


Specify standard or radius:

You cannot make a blank specification.
Specify standard or radius: standard

The command completed successfully.

VPN Client>



VPN Client>AccountList
AccountList command - Get List of VPN Connection Settings
Item                        |Value
----------------------------+---------------------------------------------
VPN Connection Setting Name |vpn-start
Status                      |Connected
VPN Server Hostname         |192.168.20.10:5555 (Direct TCP/IP Connection)
Virtual Hub                 |DEFAULT
Virtual Network Adapter Name|VPN
The command completed successfully.

VPN Client>

не забываем включит автоконнект

VPN Client>AccountStartupSet
AccountStartupSet command - Set VPN Connection Setting as Startup Connection
Name of VPN Connection Setting: vpn-start

The command completed successfully.

VPN Client>

для надежности проверим.

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ./vpnclient stop
Stopping the SoftEther VPN Client service ...
SoftEther VPN Client service has been stopped.
root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ./vpnclient start
The SoftEther VPN Client service has been started.
root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient#

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ifconfig vpn_vpn
vpn_vpn   Link encap:Ethernet  HWaddr 00:ac:7e:58:55:20
          inet6 addr: fe80::2ac:7eff:fe58:5520/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:53 errors:0 dropped:0 overruns:0 frame:0
          TX packets:57 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:6493 (6.3 KiB)  TX bytes:4379 (4.2 KiB)

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient#

о, нам не выдали IPv4, который необходим.
делаем просто.

root@proxy:/etc/network# cat interfaces
allow-hotplug vpn_vpn
iface vpn_vpn inet dhcp

проверяем

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient# ifconfig vpn_vpn
vpn_vpn   Link encap:Ethernet  HWaddr 00:ac:7e:58:55:20
          inet addr:192.168.30.12  Bcast:192.168.30.255  Mask:255.255.255.0
          inet6 addr: fe80::2ac:7eff:fe58:5520/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:159 errors:0 dropped:0 overruns:0 frame:0
          TX packets:149 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:10668 (10.4 KiB)  TX bytes:10283 (10.0 KiB)

root@proxy:~/0/softether-vpnclient-v4.19-9578-beta-2015.09.15-linux-x64-64bit/vpnclient#