When it is possible, users of unregistered (or "dirty") networks should
use the reserved addresses in
on any networks inside the PIX.
There are no specific requirements for this document.
This document is not restricted to specific software and hardware
For more information on document conventions, refer to the
Cisco Technical Tips
As discussed in RFC 1918, the addresses that you should use are shown
Class A: 10.0.0.0 - 10.255.255.255 (10/8
Class B: 172.16.0.0 - 172.31.255.255 (172.16/12
Class C: 192.168.0.0 - 192.168.255.255 (192.168/16
There are two advantages of using these numbers on the inside of the
For example, if you use the Class C range of 18.104.22.168 for network
addresses on the inside of your PIX, your computers are unable to connect to
another machine that has a legitimate IP address (such as 22.214.171.124). This is
because your hosts try to reach a machine that does not exist on the inside of