NAT type. static - Translate a specific virtual IP network to a specific real IP network. TCP, UDP and ICMP sessions originated both in real and virtual networks will be translated. dynamic - (Concurrent) Translate real IP network to larger or equal virtual IP network. TCP, UDP and ICMP sessions originated in virtual networks only can be translated and sessions originated in real networks will be rejected. A session that starts in the NAT system will be active until there will be no traffic for aging timeout period. pat - (Port Address Translation/ Single IP). Translate one real IP address to virtual IP network. TCP, UDP and ICMP sessions originated in virtual network only can be translated, sessions originated in real network will be rejected. A session that starts in the NAT system will be active until there will be no traffic for aging timeout period. transparent - In transparent mode all frames belonging to the defined IP network will be forwarded with no translation: virtual = real.