Outside and Inside NAT Addresses
Networks controlled by an organization that needs to be translated are referred to as within in the context of Network Address Translation (NAT). When NAT is set up, hosts on this network have addresses that fit in a single space (known as the local address space). Users outside the network perceive these hosts as being in a different area (known as the global address space). In a similar vein, networks that the stub network connects to but are not managed by an organization are referred to as outside. Additionally, hosts on external networks may be translated and so have both local and global addresses. The following definitions are used by NAT:
- An IP address that is given to a host on the inside network is known as an inside local address. Most likely, the address given by the Network Information Center (NIC) or service provider is an invalid IP address.
- Inside global address: A valid IP address assigned by the NIC or service provider that, to the outside world, corresponds to one or more inside local IP addresses
- The IP address of an external host as seen by an internal network is known as the “outside local address.” It is assigned from the address space that is internally routable, however, it might not always be a valid address.
- The IP address that a host’s owner assigns to it on an external network is known as the outside global address. The address is chosen from a network space or globally routable address.
Configuring NAT For IP Address Conservation in Cisco
IP address conservation is the goal of Network Address Translation (NAT). It makes it possible for private IP networks to connect to the Internet using unregistered IP addresses. Before packets are routed to another network, NAT acts as a router, typically connecting two networks, and converts the private (not globally unique) addresses in the internal network into lawful addresses. NAT can be set up to only advertise one address to the outside world for the entire network as part of this functionality. Effectively concealing the entire internal network behind one address, boosts security. NAT is frequently used in contexts with remote access because it provides the combined benefits of security and address conservation.