December 27, 2011

Simple IP Addressing Scheme for Using DHCP on your Home Wireless Network

Most small routers being sold today for wireless home networking use a set of 254 Internet Protocol (IP) addresses in the 192.168 number series for assigning network numbers to home computers that wish to access the Internet. If you are using one of these routers and had not setup some sort of security for your router, then you may be unwittingly letting your Internet connection open to a good number of devices that may connect to your network. When there are too many users connecting to your network for accessing the Internet, then you may suffer from slow network connection and it may cause your network speed to grind to a halt.

There is a way for limiting the number of devices that can connect to your network by customizing a set of private IP address numbers and letting the Dynamic Host Configuration Protocol (DHCP) server in your router allocate these numbers to the computer devices in your home network. Using a customized IP addressing scheme can make your network less attractive to would-be hackers who may have the additional work of determining what IP addresses you are using on your network.

The Internet Assigned Numbers Authority (IANA) has reserved blocks of IP addresses that can be used for private networks that are using IP for computer to computer communications. These addresses are considered non-routable and are filtered out by routers transmitting packets in the Internet. One of these blocks of numbers is the range to which had been designed for big companies that use a lot of computers in their networks. But by using an appropriate subnet mask, it is possible to carve out a very small subset of this large address block and use it for assigning numbers to home networks.

To come up with a customized IP address scheme, you first need to determine the maximum number of computers and gadgets that may be connected to your network at any one time. Then look for a table of IP address numbers for the IP address series from the Internet and find out which subnet mask to use that is appropriate for the number of users you have in mind. Then input the numbers on the DHCP settings in your wireless router configuration page. The information that you need to input are the router's IP address, its subnet mask, and the first and last number that the DHCP server is to distribute to the computers in the network.

The subnet mask is a series of four numbers similar to IP address that functions as a means of dividing a large network into smaller ones. By combining the IP address of a machine with its subnet mask, routers are able to find out to which network a computer belongs. Once the router knows the network number, it looks at its routing table to find out to which router the packet is to be transmitted next.

By using a correct subnet mask with an IP address, we can identify to which network number the computer belongs, the valid IP addresses that may be used in that network, and the broadcast address for that network. Looking up an IP address table can give us the starting valid IP address number and the last IP address number. The first address in the valid address range will be considered as the network address and the last one in the range will be treated as the broadcast address.

Say I have decided that there should be no more than six computers accessing my network at any one time. So I refer to the IP address table available in the Internet and finds out that I need to use the subnet mask. I can use any number between 0 and 255 for the remaining next two numbers after 10 and then look up the table for a network number which is the first in the range of valid numbers for the subnet. So I can come up with a new network address number say, The valid network numbers for this subnet is the range from up to My network's broadcast address will be I can now use the number as my router's IP address with the subnet mask I can then tell my router's DHCP server to distribute the rest of the numbers starting from up to to the remaining five computers in my network.

You may on the other hand feel that you need at least 14 computers connected to your network simultaneously. As per the IP address table, you need to use the subnet mask The table also gives us a number of possible address ranges that we can use. Say you have chosen to use the address range that starts from 48. So you can come up with a new network number say, Your valid address range will be from to and your broadcast address will be So in this case, your router's IP address will be and its subnet mask will be You can then give the address range to to your router's DHCP server for distribution to the computers in your network.

When you change your router's IP address, you will lose connection to your network so you will need to restart your laptop if you want to connect to your network again. But if you have setup your laptop with a static IP address, then you have to manually input a valid IP address to your laptop before you can use it in your network. In addition, you will no longer be able to access your router using the old IP address that you have been using before. You will have to use the new one that you have given to your router.

Changing the settings in your router can be tricky so before making any changes, be sure to save your router's configuration settings in your laptop. if you mess up the settings, you can always restore the router to its factory settings through a switch at the back of the router. Then access your router as you have been doing before and upload the settings that you have saved in your computer.

Read my other article on how to maintain connectivity with your wireless router when changing its IP address at: