/interface ethernet
set [ find default-name=ether1 ] name=ether1_WAN
set [ find default-name=ether2 ] name=ether2_LAN

/interface vlan
add interface=ether2_LAN name=vlan31_R1_R3 vlan-id=31

/ip address
add address=192.168.5.39/24 interface=ether1_WAN network=192.168.5.0
add address=192.168.99.1/24 interface=ether2_LAN network=192.168.99.0
add address=192.168.31.1/24 interface=vlan31_R1_R3 network=192.168.31.0

/ip dns
set servers=27.123.220.220,27.123.220.221

/ip firewall nat
add action=masquerade chain=srcnat out-interface=ether1_WAN

/ip route
add distance=1 gateway=192.168.5.254

/ip pool
add name=dhcp_pool1 ranges=192.168.31.11-192.168.31.254

/ip dhcp-server
add address-pool=dhcp_pool1 disabled=no interface=vlan31_R1_R3 name=dhcp1

/ip dhcp-server network
add address=192.168.31.0/24 gateway=192.168.31.1