WAN-Bridge

The cellular modem integrated into the router can be used in two operating modes: Router mode and Bridge mode. In router mode, the router establishes the mobile connection itself and receives an IP address on its WWAN connection (e.g., IPv4 address and/or IPv6 address/prefix), allowing a downstream network to access the Internet via Network Address Translation (NAT). The IP address assigned by the provider is shared with multiple LAN clients in this case.

In bridge mode, the router acts as a simple network bridge and forwards all IP packets from the mobile network to exactly one downstream device. This device therefore receives the IP address assigned by the provider directly and must establish the WAN connection (via DHCP) to the provider and handle NAT and routing for the internal network.

Bridge mode is useful when the device is intended to operate purely as a modem, for example, to avoid double NAT in a router cascade. The WWAN bridge mode is conceptually comparable to the bridge mode of DSL modems.

The device providing bridge mode itself does not have an IP address on the WWAN interface and therefore cannot establish a direct connection to the mobile network, as data packets are transparently forwarded. If the device is to be managed via the LMC, for example, Internet access must be established through an alternative route.

Only the first client that connects to the device in bridge mode receives the IP address assigned by the mobile network. Packets from the cellular modem are passed on without VLAN tagging.

It is recommended to configure ICMP polling on the WAN connection of the downstream device, as it is not possible by design for the modem to notify the downstream device of a connection loss or address change. ICMP polling allows the downstream device to detect an interruption in the mobile connection.