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Chapter 4: Serial Port, Device and User Configuration
4.12 IP Passthrough
IP Passthrough is used to make a modem connection (e.g. the Appliance’s internal cellular modem) appear like a regular
Ethernet connection to a third-party downstream router, allowing the downstream router to use the Appliance’s modem
connection as a primary or backup WAN interface.
The appliance provides the modem IP address and DNS details to the downstream device over DHCP and transparently passes
network traffic to and from the modem and router.
While IP Passthrough essentially turns an Appliance into a modem-to-Ethernet half bridge, some specific layer 4 services
(HTTP/HTTPS/SSH) may still be terminated at the Appliance (
Service Intercepts
). Also, services running on the Appliance can
initiate outbound cellular connections independent of the downstream router.
This allows the Appliance to continue to be used for out-of-band management and alerting while in IP Passthrough mode.
4.12.1 Downstream router setup
To use failover connectivity on the downstream router (aka
Failover
to
Cellular
or
F2C
), it must have two or more WAN
interfaces.
Note:
Failover in IP Passthrough context is performed entirely by the downstream router, and the built-in out-of-band failover
logic on the Appliance itself is not available while in IP Passthrough mode.
Connect an Ethernet WAN interface on the downstream router to the Appliance’s Network Interface or Management LAN port
with an Ethernet cable.
Configure this interface on the downstream router to receive its network settings via DHCP. If failover is required, configure the
downstream router for failover between its primary interface and the Ethernet port connected to the Appliance.
4.12.2 IP Passthrough pre-configuration
Prerequisite steps to enable IP Passthrough are:
• Configure the
Network Interface
and where applicable
Management LAN
interfaces with static network settings
o Click
Serial & Network: IP
o For
Network Interface
and where applicable
Management LAN
, select
Static
for the
Configuration Method
and
enter the network settings (see the section entitled
Network Configuration
for detailed instructions)
o For the interface connected to the downstream router, you may choose any dedicated private network – this network
will only exist between the Appliance and downstream router and will not normally be accessible
o For the other interface, configure it as you would per normal on the local network
o For both interfaces, leave
Gateway
blank
• Configure the Appliance modem in
Always On Out-of-band
mode
o For a cellular connection, click
System: Dial: Internal Cellular Modem
o Select
Enable Dial-Out
and enter carrier details such as
APN
(see the section entitled
Cellular Modem Connection
for detailed instructions)