FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
dkoprusak
Staff
Staff
Article Id 424342
Description This article describes steps for enabling DHCP relay over the built-in modem interface (WWAN) for FortiGate-40F-3G4G.
Scope FortiGate-40F-3G4G.
Solution

The built-in modem can be set up to enable DHCP relay via the AT commands:

 

  1. To enter the AT command interface:

 

diagnose system modem com /dev/ttyusb2

 

 

  1. To unlock the custom modem AT commands:

 

#at!entercnd="A710"

 

 

  1. Check if the DHCPRELAYENABLE is enabled (in the output below, the DHCPRELAYENABLE is disabled):


#at!custom?
!CUSTOM:
GPSENABLE 0x01
GPSLPM 0x01
IPV6ENABLE 0x01
UIM2ENABLE 0x01
SIMLPM 0x01
USBSERIALENABLE 0x01
QXDMLOGENABLE 0x01

 

  1. Enable the DHCPRELAYENABLE with the AT command:

#at!custom="DHCPRELAYENABLE",1

 

  1. Check if DHCPRELAYENABLE is enabled:

at!custom?
!CUSTOM:
GPSENABLE 0x01
GPSLPM 0x01
IPV6ENABLE 0x01
UIM2ENABLE 0x01
SIMLPM 0x01
USBSERIALENABLE 0x01
DHCPRELAYENABLE 0x01 <----- Now enabled.
QXDMLOGENABLE 0x01

 

See the AT Command Reference.

 

As of FortiOS 7.4.0, a new CLI setting was added to allow DHCP relay packets flow through the modem interface (WWAN):

 

config system lte-modem
(lte-modem) # set dhcp-relay disable/enable
(lte-modem) # end

 

The status can be verified via the following process:

 

diagnose sys lte-modem traffic-status
LTE Modem traffic status:
DHCP relay packets: blocked <-----

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