Functions in the NAT (Network Address Translation) A router connecting two networks together; one designated as inside is addressed with either private or obsolete addresses that needs to be converted into legal addresses before packets are forwarded onto the other network (designated as outside). An IETF(Internet Engineering Task Force) standard that allows an organization to present itself to the Internet with one address. NAT converts the address of each LAN node into one IP address for the Internet and vice versa. It also serves as a firewall by keeping individual IP addresses hidden from the outside world. See proxy server. section are used to configure certain aspects of the NAT facility. These facilities are Aliases, Inbound Tunnels, Static Address Mapping A GNAT Box facility that allows an internal IP address or subnet to be statically mapped to an external IP address during the network address translation process. Typically, mapping is used with targets on the External network interface. Mapping is not useful unless IP aliases have been assigned to the target network interface, since by default all IP addresses on the Protected network are dynamically assigned to the real IP address of the outbound network interface. and Timeouts.
Network Address Translation translates an IP address behind the firewall to the IP address of the External Network The External network is the unprotected network for which no network address translation is performed. The External network is typically connected to the Internet. However, GNAT Box can also be used internally on private networks as an intranet firewall. If connected to the Internet, the external interface must have a registered IP address. GNAT Box provides no security for hosts located on the External network. See Protected and Private Service Networks. interface, effectively disguising the original IP address and making it possible to use a non-registered IP address within the Protected Networks and the PSNs, while still presenting a registered IP address to the External Network (typically the Internet).
The NAT facility used in GNAT Box System Software is active by default. NAT is applied to outbound packets from a Protected to an External Network; from a Protected Network The Protected network is the network hidden behind the GNAT Box system. The term Protected network is used by GTA to refer to the network directly connected to the GNAT Box system. All features and attributes associated with this network also apply to all networks connected to the Protected network. All hosts and IP addresses used on this network are hidden from the External and Private Service networks. Hosts on the Protected Network are by default not accessible from the External network or PSN network. The Tunnel facility can be used to allow external access to hosts and services on this network. to a PSN; from a PSN to an External Network; from one Protected Network to another Protected Network; and from one PSN to another PSN.
NAT is available in two forms: dynamic and static, referred to as Default NAT and Static Address Mapping. NAT can be bypassed using IP Pass Through.