# more /etc/pf.conf                                                            
ext_if=ne3 #DHCP
int_if=ne4 #10.37.129.1

nat on $ext_if from $int_if:network to any -> ($ext_if)


block in on $ext_if
pass in on $ext_if inet proto tcp from any to any port 22
pass out on $ext_if from any to any