D-Link DI-206 - Manual (Page 99)

DI-206 ISDN Remote Router
Configuration and Management 87
request is 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.