HOW TO: Configure IP Pass-through mode on Digi TransPorts

Overview
 
This guide will describe how to configure IP Pass-through on the TransPort to hand the Mobile IP address to 1 Ethernet connected device behind the TransPort, so that the TransPort becomes transparent in the setup, and the Mobile IP becomes the IP of the attached Ethernet device (acts similar to a Cable/DSL modem in this mode).
 
Assumptions
 
This guide assumes that the Ethernet device that needs the Mobile IP address is directly connected to the Digi TransPort via an Ethernet interface, and is in DHCP mode to obtain an IP address automatically.
 
IP Pass-through Setup
 
1)  Log into the WebUI, and navigate to Configuration – Network > IP Passthrough.
 
NOTE:  Use the below screenshot as a reference for steps 2-9
 

 
2)  Check the box for Enable IP Pass-through.
 
3)  Set the Local interface to bind the Pass-through connection to.  This is usually the first Ethernet interface on the TransPort (Eth 0).

4)  Set the WAN PPP interface to 1 to use the Mobile interface as the shared interface.
 
5)  Select the Ethernet DHCP Mode.  There are 2 options:
 
a)  Normal/24 bit mask – On the Ethernet connected device, the TransPort sets the Mobile IP as the IP of the Ethernet device, sets the Subnet Mask to 255.255.255.0, and sets the Default Gateway to the Mobile IP with the last octet being a 1.  Example:  If the Mobile IP is 166.130.108.94, the Default Gateway would be 166.130.108.1.  The only exception to this rule is if the Mobile IP ends in a .1, then the Default Gateway will be a .2 instead.
 
b)  Fixed IP Address/32 bit mask – On the Ethernet connected device, the TransPort sets the Mobile IP as the IP of the Ethernet device, sets the Subnet Mask to 255.255.255.255, and sets the Default Gateway to 192.168.1.1.  This mode does not use NAT, where the normal mode above does.  This option is typically not used.
 
6)  Set the DHCP Lease Time for the length of the DHCP lease the TransPort will hand to the Ethernet device.
 
7)  Selection the pinholes to use under Pinhole Configuration.  Pinholes are ports that will still be stopped at the TransPort, instead of being passed through to the Ethernet connected device.

NOTE:  If no pinholes are checked, you will lock out all access to the TransPort, and it will need to be factory defaulted to gain access back in.
 
8)  (Optional)  It is possible to setup custom ports and protocols to stop at the TransPort.  Fill these in under the Other Ports and Other Protocols fields.
 
9)  Click Apply and Save the settings.
 
NOTE:  If connecting via Ethernet and after clicking Apply, it is possible that connectivity to the TransPort will be lost until the Ethernet device renews its IP address to pull in the Mobile IP, so the settings will not be saved until you log back into the TransPort to save them.  Once the new IP is assigned, it is possible to connect back into the TransPort via an open pinhole using the Default Gateway assigned to the Ethernet device, and save the settings once in the TransPort.