FRITZ!Box 4020 Service - Knowledge Base
Can the FRITZ!Box USB remote connection be used over VPN?
The FRITZ!Box remote connection software cannot be used to access USB devices connected to a remote FRITZ!Box over a VPN connection. The FRITZ!Box USB remote connection communicates with the FRITZ!Box using multicast messages and broadcast messages that can only be transmitted within a local IP network. Therefore, you cannot use the FRITZ!Box USB remote connection over VPN connections.