DI-1162 Remote Access Router
made. Since there are only 5 global IP addresses in the example above, there can only be 5 mappings at any one time. In other words, much like static NAT, only 5 local machines can access the Internet at any one time. However, contrary to static NAT, the router will discard the mapping between the global and local IP addresses after a certain length of time (which is quite long so rarely happens), or after the session is finished (an example of a session is when requesting a web page, the entire page has completed downloading). The most common implementation of NAT is to define a range of dynamic addresses to be used by hosts, but assign static addresses to your servers if you wish for them to be accessible from outside your network.
Setting Local IP Addresses
When implementing NAT and thus creating a private network that is isolated from the Internet, you can assign any IP addresses to host computers without problems. However, the Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of IP Addresses specifically for private networks:
Class | Beginning Address | Ending Address |
A | 10.0.0.0 | 10.255.255.255 |
B | 172.16.0.0 | 172.31.255.255 |
C | 192.168.0.0 | 192.168.255.255 |
It is recommended that you choose local IP addresses for use with NAT from the private network IP addresses in the above list. For more information on address assignment, refer to RFC 1597, Address Allocation for Private Internets and RFC 1466, Guidelines for Management of IP Address Space.
80 | Configuration and Management |
