How to Access a host behind a server over VPN (IP Forwarding)

cisco-vpnip-forwardingmasqueradepingvpn

I have a Ubuntu server (172.10.200.11) and many remote terminal units with simcards and each individual simcard operator using different IP pool such as 10.57.0.0/16 for OP-A, 10.112.0.0/16 for OP-B, etc.

In the server actually i am using a routing table to be able to access the remote terminal units on diffent IP pools. Without this routing table i have no access to the IP pools.
For instance :
10.57.0.0/16 using gw 172.10.238.1
10.112.0.0/16 using gw 172.10.238.2
10.155.0.0/16 using gw 172.10.238.3

And…

Actually i am using "Cisco VPN Client" to access my server IP from outside of datacenter. For this purpose i am making a connection to VPN gateway using "Cisco VPN CLient" application then trying to ping my server's IP 172.10.200.11

I can do the following things successfully from my laptop after my VPN Connection established to VPN Gateway:

  • Establish Remote Desktop connection the server's IP:172.10.238.3
  • Establish SSH connection from my laptop to the server's IP:172.10.238.3
  • ICMP ping to the server's IP:172.10.238.3
  • Traceroute to the server's IP:172.10.238.3

For checking the connection (up or down) status of Remote Terminal Units i am connecting to the server via SSH or Remote Desktop then trying to ping to the IP address of Remote Terminal Unit.

Everything is OK until here but this way consumes too much bandwidth especially in case if connect via Remote Desktop connection.

  1. Connect to VPN Gateway using "Cisco VPN Client" from the laptop
  2. Establish a Remote Desktop connection to server's IP
  3. Open Browser in the server on Remote Desktop Connection.
  4. Enter Remote Terminal Unit (RTU)'s IP (10.155.1.22) on the browser and do what you want!
  5. Successfullu establish an ICMP ping to the RTU's IP address (10.155.1.22) in a terminal screen on Remote Desktop or in a SSH connection session.

But i want to do following:

  • Connect to VPN Gateway using Cisco VPN Client from the laptop
  • Open Browser in the laptop
  • Enter Remote Terminal Unit's IP (10.155.1.22) on browser and do what you want!
  • Successfully establish an ICMP ping to the RTU's IP address (10.155.1.22) in a shell/terminal screen on my laptop (NOT in Remote Desktop)

Restrictions:

  • Actually i have no right to change the VPN gateway settings. But i can
    only change the server settings to achieve this.

Is there any way to do this? I know it exist but my mind confused.
First i have installed Hamachi but this way give me access to server without need of VPN connection. But still i can not directly ping to RTU IP's from my laptop. It did not resolved my problem.

In technically i want to use my server act as a "router" to route/forward incoming requests from my laptop (ICMP & IP packets) to the RTU's IP.

I have researched about how to enable IP MASQUERADE or IP FORWARDING on Ubuntu 16.04. If i am right -technically- it needs 2 NICs or 2 Different IPs on the machine. But i have only one IP (Bonded) on my server.

I need to reach directly to the RTU IP addresses from my laptop and my server should be acting as a router/gateway or etc. to achieve this.

Is there anybody can explain me step-by-step how to do this on Ubuntu?

Click to see picture of my system diagram

Best Answer

You need to add routes for the 10.57.0.0/16 etc. networks to your VPN client so that they are routed via the server IP. You should be able to add the routes in your VPN server settings. I don't know details on how they would be added in Cisco VPN server.

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