The following commands run on the USG will use the pppoe1 WAN for the two source addresses specified.
configure
set firewall modify LOAD\_BALANCE rule 2500 action modify
set firewall modify LOAD\_BALANCE rule 2500 modify table 5
set firewall modify LOAD\_BALANCE rule 2500 source address 192.168.0.102
set firewall modify LOAD\_BALANCE rule 2500 protocol all
set firewall modify LOAD\_BALANCE rule 2501 action modify
set firewall modify LOAD\_BALANCE rule 2501 modify table 5
set firewall modify LOAD\_BALANCE rule 2501 source address 192.168.0.115
set firewall modify LOAD\_BALANCE rule 2501 protocol all
set protocols static table 5 interface-route 0.0.0.0/0 next-hop-interface pppoe1
commit;save;exit