all_node="172.31.255.1/32"
edu_net="192.168.4.0/24"
allow_ext_tcp="{22}"
allow_ext_udp="{161}"
allow_int_tcp="{22,ntp,3128}"
allow_int_udp="{53,ntp,161,12345}"
allow_int_udp_any="{67}"

ext_if="vr0"

# Nat the internet
nat on $ext_if from $edu_net to any -> ($ext_if) 

pass on vr0
pass on tap0
pass on ue0