Why can’t I Access or Discover Certain Devices Over VPN？

If you configure your router as a VPN Server and try to remotely access LAN resources, or manage devices over the Internet, you may encounter the following issues:

Case One: Unable to Access Certain LAN Devices

If you're having trouble accessing certain LAN devices while connected to a VPN Server, there could be a few reasons for this. To check if a device is accessible, you could try using the ping command. How to Use the Ping Command

1. A possible reason is that the firewall settings on the devices you're trying to access are blocking incoming traffic from VPN connections. For example, Windows PCs typically block remote traffic from VPN clients, since their IP addresses are from a different subnet.

To resolve this issue, try disabling the firewall temporarily to see if that resolves the issue. If it does, you can create a new inbound rule to allow traffic from the specific IP address of the VPN client, if you still need the firewall enabled. Please refer to Create an Inbound Port Rule (Windows)

2. Some devices may not be compatible with VPN networks, or may require special configuration. This can include older devices or devices with specific network requirements. If so, port forwarding may be used as an alternative solution. Port forwarding: how to set up virtual server on TP-Link wireless router? It is also recommended to contact the support team of that device for assistance as needed.

Case Two: Unable to Discover Some Network Devices

If you open File Explorer on a Windows computer and click on the "Network" icon in the navigation pane, you can view a list of devices that are visible on your local network, such as computers, printers, routers, NAS, digital signage displays, and other network devices.

However, when your device is connected via VPN connection, you may not be able to see them. The reason is that the network discovery packets which allow devices to advertise their presence can’t pass through VPN tunnels. In this situation, you can access devices on your local network by using their IP addresses directly, rather than relying on network discovery protocols to find them. 

For example, if your PC is on the same LAN as a NAS, you can easily find it. However, if you are using a remote PC as a VPN client, you may not be able to find the NAS but can still access it by visiting smb://IP of NAS or ftp://IP of NAS in File Explorer.