Configure TCP/IP over USB with internet sharing

This guide shares a host's internet connection with a PAX terminal over USB, and covers giving the terminal internet over Ethernet. For the overall picture — topology, ports, and the terminal-side setup — start with Connect your terminal to your POS.

Step 1: Enable the USB network on Terminal

1. Open NTMS Agent, which holds all USB configuration.
2. Go to Advanced settings and enter the password 4315.
3. Open USB Mode Settings, select USB-PC (RNDIS reverse) or USB ECM-HOST tethering, and save. This is what makes the terminal able to communicate with POS.

Set up the USB (RNDIS) connection for Windows (Linux here)

USB tethering (RNDIS) gives a reliable, low-latency link. These steps share your computer's internet connection with the terminal over USB.

Step 1 — Configure your computer

Open the Network Connections window (Start → type View network connections, or Control Panel → Network and Internet → Network and Sharing Center → Change adapter settings). A new connection appears — here, Ethernet 3:

Right-click the connection that has internet access, open Properties → Sharing, and share it with the payment terminal connection. Here, NVP_OPT has internet access:

Select the payment terminal RNDIS connection:

Open the RNDIS connection's Properties → IPv4 and configure it with the static IP 192.168.42.1, netmask 255.255.255.0. This address is the gateway you set on the terminal during terminal-side setup.

The terminal now has internet access.

Step 2 — Make internet sharing persistent

Keep the shared connection working after the computer reboots. Open Windows PowerShell with administrative privileges:

Run (this is a single command):

New-ItemProperty -Path HKLM:\Software\Microsoft\Windows\CurrentVersion\SharedAccess -Name EnableRebootPersistConnection -Value 1 -PropertyType dword

Then set the Internet Connection Sharing service to start automatically:

1. Open Services (Start → Services, or Windows + R → Services.msc).
2. Open the Internet Connection Sharing (ICS) service.
3. Set its startup type to Automatic.

Set up the USB (RNDIS) connection for Linux

This guide shares a Linux host's internet connection with a PAX A35 terminal over USB, so the terminal can reach Market Pay through the host. The examples use Ubuntu; the commands apply to any Debian-based distribution. For the overall picture — topology, ports, and the terminal-side setup — start with Connect your terminal to your POS.

Phase 1 — Prepare the connection

Step 1 — Identify the interfaces

Connect the A35 to the host by USB. Run ifconfig and note two interfaces:

• usb0 — the new virtual NIC that bridges to the A35.
• Your active internet interface — for example wlp0s20f3 for Wi-Fi, or an eth* / enp* name for wired.

Step 2 — Disable auto-connect on the USB interface

In the Ubuntu desktop, stop NetworkManager from managing the USB link so it doesn't fight your manual configuration:

1. Open Wired Settings for the USB virtual connection.
2. Turn off Connect automatically.
3. Apply the change, then drive the interface from the terminal with the commands below.

Phase 2 — Configure network routing

Step 3 — Enable IP forwarding

Let the host route traffic between interfaces:

sysctl -w net.ipv4.ip_forward=1

Step 4 — Configure NAT with iptables

Masquerade the terminal's traffic behind your internet interface. Replace wlp0s20f3 with the interface that has internet access:

iptables -t nat -A POSTROUTING -o wlp0s20f3 -j MASQUERADE

Step 5 — Assign the USB interface IP

Give usb0 the gateway address the terminal routes through:

ifconfig usb0 192.168.42.1

This 192.168.42.1 must match the gateway you set on the terminal, so the A35 (default 192.168.42.129) can route its traffic through the host.

Verify the connection

Once the host is configured, confirm the terminal has internet from the Pay On Site Diagnosis screen — see Verify connectivity in the main guide.

Next steps

• Back to the overview — Connect your terminal to your POS.
• Configure the terminal's IP and firewall access — Configure your network.