Basic NAT is a set of IP addresses to another group of IP address technologies, providing transparent routes for terminal hosts. Network Address Port Conversion (NAPT) is a method of translating group network addresses and corresponding TCP / UDP ports into a single network address and its corresponding TCP / UDP port. Therefore, compared with traditional NAT, the current two operations provide an integral mechanism for connecting internal networks and external networks from a global unified addressable address.
It is possible for confidentiality, such as: Users don't want external network users to know their own network internal structures; it is possible for the legal Internet IP address of the user, and the internal network users have a lot of IP addresses, making the internal network IP address It is not available for external networks, so this requires IP address conversion by means of NAT. The topology of the network outside the local area is changed in a variety of ways: the company replaces suppliers; recombinant companies' backbone networks or suppliers merged or tether. Once the external topology changes, the address assignment of the local code must also be changed to reflect the external change. Since these changes are concentrated in the address translation router, the LAN users don't know these changes. The basic address conversion allows the host to transparently access the external network from the internal network, and allow the selected local host from the outside. For an agency, its network is mainly used for internal services, this configuration is only available for external access.
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