We have an AdLink industrial PC running Ubuntu sitting behind an Asus broadband router (RT N12) at a customer's home, and I'm having trouble accessing it from outside the network. Details:

  • When the PC was connected to an external static IP on our office, I was able to ping it as well as VPN into it using OpenVPN over port 1194 via TCP, then, once VPN'd in, was able to access an application on it via HTTP on port 8088
  • We enabled VPN on the router and port forwarded 1194 to the PC IP's 1194 as well as 1022 to the PC IP's 22 for SSH access and 8088 to the PC IP's 8088 The router uses PPTP for VPN. I was able to successfully connect via the built-in PPTP provider on my windows 10 box
  • Initially, the router created an internal private IP address in the 192.168 range, which was the same as my internal home network behind my internet router, so we adjusted the customer's router to use the 172.16 address range. The AdLink PC was able to obtain an IP address in that 172.16 range behind the customer's router
  • When I am VPN'd in to the router, I can ping the router's internal IP address but not the AdLink PC's internal IP address
  • After I ping the router, I can run arp -a in a command prompt and see the AdLink IP address under the Interface with the customer router's IP address
  • I cannot ping or ssh or browse to the HTTP service at 8088 on the PC
  • Someone on site, who was connected to the router directly via a network cable, was able to ping and ssh into the machine
  • The router has a network ping feature, and it can ping the attached PC

Outside the port forwarding, router VPN setup, and DHCP address range change, I'm not sure what else try to obtain a connection to the PC. Any other suggestions are welcome. I'm a software engineer by trade and do not know this kind of networking in any depth.

  • I don’t understand your last bullet (‘‘Someone on site was able to connect to the machine while on the local network’’).  Can you rephrase that?   Please do not respond in comments; edit your question to make it clearer and more complete. – G-Man Says 'Reinstate Monica' Nov 13 '17 at 20:00

Several things were wrong:

  • Client IP list overlapped with the DHCP internal IP list
  • VPN access through the firewall needed to be enabled via specific port forwarding
  • DMZ had to be enabled

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