All computers and other devices that you have connected to your network, either by WiFi or by physical Ethernet connection will be allocated an address by your router. The address is used by the devices and the router to identify one another so that information can be sent and received by the intended machine.

The router will take an address that is often referred to as the Default Gateway address; this means that it is the address to which all traffic is sent and it will then decide how to deal with it. For example, if you are browsing the web and you open a page, your computer will send a request to the internet for that page, but because you are not connected directly to the server that hosts the page you want your request will be sent to the Default Gateway address, your router, which will then forward the request to servers on the web. They will in turn send the page back to your router which will then forward the page back directly to your computer. If you want to send a page to a printer that is on your network, you will have used the driver software to set up the printer and the page will be sent directly to the printer’s address.

When you set up your router you can decide whether you want to fix the address of your computer (Static address) or just let the Router issue the addresses (Dynamic address). In most cases it is simplest to go with the Dynamic address allocation, referred to as DHCP (Dynamic Host Control Protocol); this means that each time you connect to your network you could be allocated a different address, which does not really matter and if you have lots of users is a more efficient way of using your address space. However some devices on your network are better off using the same address all the time, items such as printers and hard drives. You can allocate a portion of the address allocation to be kept for Static addresses, leaving the rest for Dynamic allocation.

In the example shown the Default Gateway address is shown as 192.168.168.1, and the DHCP pool is show as being from 192,168.168.64 – 100. This means that you can automatically allocate addresses to 37 PCs, laptops and phones. All the addresses from 192.168.168.2 – 63 are Static and can be manually given to printers, hard drives or specialist servers.

But how to restrict access on to the network? The easiest way is to use the MAC address filter. A MAC address is a 48 bit unique identifier that is given to every single computer connection. It is burned into your laptop, once for the Ethernet connection and again for the WiFi connection. You can find out what your MAC address is by using the command tool found in Accessories and typing ipconfig /all. This will display a whole host of info about your computer and its connections, but the information you are interested in is Physical Address or MAC address.

You can take this address and add it to a list on the Router so that you can control who has access to your network. By adding the address you restrict access to only those who have given you their MAC address. Other PCs or phones will not be able to use the router.

As with all things, MAC filtering is not fool proof and an unscrupulous person could get hold of your MAC address and then clone it so they could gain access to your network. But as a simple method of restricting access it is a good start. Just remember to remove the MAC addresses of old PCs or you might end up with a massive list that becomes unmanageable.

The reserved Static addresses can now be allocated to devices such as a network printer. To do this you need to follow the instructions on the printer and we will look at that next time, using an HP printer as the example.

Richard Sparkes is a specialist in mobile communications technology

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