IP Addresses & MAC Addresses

When identifying a device on a network we use two different types of address : IP address and MAC address. whilst it may seem sensible just to use one type of address, the IP address and MAC address are used for different purposes and often in combination.

As data packets are set up to be sent across the network, both the IP address and MAC address of the sender and recipient added to the data packet in order to be able to reach the required destination. There’s more information about how data packets are created on the network layers page.

network interface cardEvery device that is able to connect to a network contains a network interface card. This internal piece of hardware allows the device to perform a handshake with main network connection device (usually a router or wireless access point). Part of this handshake is to provide the device’s MAC address and for the router to assign the device and IP address within the network.  

IP Addresses

ip addressIP addresses are made up of a number of 8 bit binary numbers usually represented in denery separated by full stops. There are two types of IP address : IPv4 which uses four 8 bit binary numbers and IPv6 which uses six 8 binary numbers.

When using the internet, the IP address of the network router is visible to the webserver and called the public IP address.

For example, your public IP address is:

IP addresses are known as dynamic addresses. This is because the router will assign the next available IP address to the device as it joins the network and this address is then removed from the device as it leaves the network. This means that even though there are a finite number of addresses available, they can be reused as devices join and leave.

MAC Addresses

laptop wifiThe MAC address, or Media Access Constrol address of a device is a static address. This means but the MAC address for the device never changes as it is hard coded into the network interface card.

Because each MAC address must be completely unique, they are often much longer than IP addresses and are often represented using hexadecimal instead of denary.

One useful part of having a MAC address is that it allows the network to uniquely identify any device. Should that particular device (or user) have caused an issue in the past, the MAC address can be used by the network manager to ban them from connecting to the network.

Creating this list of banned MAC addresses is known as MAC address filtering and can be set up by using a blacklist which holds a list of banned MAC addresses or by creating a white list which holds a list of allowed MAC addresses.

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