If NAT is switched on for an interface, this table contains an entry for each session running over the interface. Table entries are creates by the system whenever a valid session is established. A session may be either a tcp connection, a udp connection or an icmp connection with icmp-echo messages (ping). A valid session is either an outgoing session or an incoming session specified in the ipNatPresetTable. Everything behind an interface with NAT enabled is called outside. The BRICK itself and all networks connected to it via interfaces without NAT are called inside. Table entries are removed after timeout. This timeout is specified by ipExtIfNatOtherTimeout for UDP and ICMP sessions. specified by ipExtIfTcpTimeout for TCP sessions 16 seconds for closed TCP-sessions (FIN has been received and acknowledged in both directions).