Technical Tip: Gateway configuration for DHCP and PPPOE SD-WAN members

Configuration example in CLI:

config system interface
    edit "port4"
        set vdom "root"
        set mode dhcp
        set allowaccess ping https ssh http telnet fgfm
        set type physical
        set lldp-reception enable
        set role wan
        set snmp-index 4
    next
end

If an interface is configured to use DHCP or PPOE and added to an SD-WAN interface, select 'Dynamic' for Gateway, as the gateway is learned dynamically through the DHCP process.

The SD-WAN member configuration should be:

Through CLI:

FGT-HUB # config system sdwan

FGT-HUB (sdwan) # config members

FGT-HUB (members) # edit "1"

FGT-HUB (1) # show
config members
    edit 1
        set interface "port4"
        set zone "underlay"
    next
end

Extra caution should be taken if the DHCP interface is added first and is the only underlay interface, as adding the DHCP interface as an SD-WAN member will erase the dynamically added default route added through the DHCP process. To overcome this, before adding the DHCP interface as an SD-WAN member, it is necessary to add a default static route pointing to the DHCP interface:

Through CLI:

FGT-HUB # config router static

FGT-HUB (static) # edit "2"

FGT-HUB (2) # show
config router static
    edit 2
        set device "port4"
        set dynamic-gateway enable
    next
end

After adding the DHCP interface to SDWAN, you can modify the created default static route to use the SD-WAN interface. The SD-WAN interface cannot be used in routing before adding a member.