Digi X2 - Manual (Page 94)

C o n f i g u r a t i o n t h r o u g h t h e w e b i n t e r f a c e
9 4
IP pass-through settings
There are many application scenarios where a router is used to decide upon alternative
routes using a primary and a secondary (or backup) interface. In many of these
configurations, the router is required to use a public IP address as assigned by the network
over which it is communicating. This requirement is mostly owing to the router needing to
establish a VPN tunnel over that interface and using the public IP address as part of the
VPN authentication. (For more on VPN tunnels, see page 99.)
The IP pass-through feature allows a Digi device device to provide bridging functionality
similar to that of a cable or DSL modem, where the Digi device becomes “transparent” to
the router or connected device. In this case; the router’s WAN interface believes it is
connected directly to the mobile network and has no knowledge that the Digi device is the
mechanism providing that connectivity.
How IP pass-through works
A Digi device configured for IP pass-through, such as a ConnectPort WAN or Digi
Connect WAN, passes its mobile IP address directly through and to the Ethernet device
(router or PC) to which it is connected through the Ethernet port. From the perspective of
the connected device, the Digi device essentially becomes transparent (similar to the
behavior of a cable or DSL modem) to provide a bridge from the mobile network directly
to the end device attached to the Digi device.
Since the mobile network address is effectively “passed-through” to the local device
connected to the Ethernet port of the Digi device, all network access to it is bypassed, with
some specific exceptions.
Here is an example of a Digi device configured for IP pass-through in a network with a
third-party router.