MAC address is stored as a 48-bit string of digits and letters in hexadecimal system (digits from 0 to 9 and letters from A to F). Half of the MAC address, i.e. the first 6 characters (24 bits) determines the manufacturer of the network adapter installed in the device. The remaining characters are a unique device identifier. MAC address is denoted using character pairs, each pair separated with a dash or a colon. The manufacturers often specify the MAC address as a series of digits and letters.
Unlike IP addresses, MAC addresses are assigned to a specific network device. It guarantees that the website will be displayed on the computer the search was initiated and not on a different computer connected to the same network or subnetwork with the same IP address.
For normal users, MAC address is not important. However, it is a key factor in operation of even the most basic computer network. For example, a screenshot of the configuration page of TP Link TL-WR1042ND router available in Delta offer is shown below (Fig. 1). It is a budget, easy to use router offering a variety of configuration options, e.g. MAC address filtering. The screenshot shows that the wireless network can be accessed by three devices included on the MAC address list (Allow). Select ‘Deny the stations specified by any enabled entries in the list to access’ to reverse the situation and allow access to all devices except those on the list (e.g. black list).
Fig. 1. TL-WR1042ND router configuration page in ‘Wireless MAC Filtering’ tab
Using this option significantly improves the network security. Even if the WAN password known, the intruder will not be able to connect to the network until the MAC address is added to the list of authorized devices. It applies to all devices with Wi-Fi connectivity, including phones, tablets etc.
Another example of an important role of the MAC address is a simple home network including two PCs, a printer and a tablet (Fig. 2).
Fig. 2. Example home network with fixed IP address for a printer and random IP addresses for other devices assigned by the router depending on the log-in order.
To make sure the printer is always visible to other devices, its MAC address is assigned a fixed IP address 192.168.1.100. In case of an unexpected router restart (e.g. power failure), the printer is assigned the same address and not a random address assigned by DHCP server to other devices. Assigning the IP addresses to the MAC addresses allows to manage the network devices.