If you obtain Internet access from a DSL or cable provider, you are likely using a connection device (commonly and incorrectly called a “modem”) provided to you by that service provider. In many cases, you have little to no control over this device in terms of changing settings—especially security-related settings. Thus, many will resolve that issue by installing their own wireless access point (WAP) in order to gain full access to and control over the security of their Internet link. This setup would typically be organized as follows: miscellaneous systems — WAP — DSL/cable device — Internet.
Once the WAP is installed, you can fully configure the settings of the network connecting your systems to the Internet. Thus, you are no longer relying on the security (or lack of security) of the device provided by the DSL or cable company.
However, some find that once they install their WAP, their system loses connectivity. Often, this is due to the WAP attempting to double NAT the same network addresses. NAT, or network address translation, is the technology that converts one set of network addresses into another. Often this is used to convert private IP addresses into one or more public addresses in order to support Internet connectivity from the private network, while making it difficult for outside entities to reach into the private network from the Internet. Often, the network address range used by default from a DSL or cable device is that of 192.168.1.1–192.168.1.254. If the WAP you deploy is also using that network address range, the double NATing of the same address space will be attempted. This causes a failure in the NATing and routing processes, which means no traffic will traverse your WAP in either direction.
To resolve this issue, adjust the settings of your WAP to use a different private IP address range for the LAN and wireless networks it will support. This could be as simple as using 192.168.2.1–192.168.2.254. But, you can get creative and use any network range from the official RFC 1918 document that designates the private IP address ranges. These are: