PC-based routers OpenBSD 2.x with IPF was very flexible. The firewall language was ingenious compared to Cisco IOS. OpenBSD+IPF: map fxp0 192.168.1.0/24 -> 171.69.233.208/28 portmap tcp/udp 10000:65000 Cisco IOS: ip nat pool net-20 171.69.233.208 171.69.233.223 netmask 255.255.255.240 ip nat inside source list 1 pool net-20 ! interface Ethernet0 ip address 171.69.232.182 255.255.255.240 ip nat outside ! interface Ethernet1 ip address 192.168.1.94 255.255.255.0 ip nat inside ! access-list 1 permit 192.168.1.0 0.0.0.255 access-list 1 permit 192.168.2.0 0.0.0.255