#TechExchange: How IP and MAC Addresses Work Together During Data Transmission


The technical setup behind your device’s ability to access the Internet depends on the close working relationship between IP Addresses and MAC Addresses. These special addresses or binary codes are mapped together in a very unique way so that your device is able access data over the Internet. In today’s #TechExchange, I am going to explain and define the relationship between these two unique addresses so as to reveal how your device is able to initiate an Internet connection.

By Cisco Eng. Shingie Lev Muringi 

There are two primary addresses assigned to a host device(either your phone, tablet, laptop etc) as said above, the Physical address (the MAC address) and the Logical address (the IP address). 

Both the MAC address and IP address work together to identify a device on the network. The process of using the MAC address and the IP address to find a computer is similar to the process of using a name and address of an individual to send a letter.

A person’s name usually does not change. A person’s address on the other hand, relates to where they live and can change anytime due to migration.

Similar to the name of a person, the MAC address on a host does not change; it is physically assigned to the host Network Interface Card (NIC) and is known as the physical address. The physical address remains the same regardless of where the host is placed.

The IP address is similar to the address of a person. This address is based on where the host is actually located. Using this address, it is possible for a frame to determine the location of where a frame should be sent. The IP address, or network address, is known as a logical address because it is assigned logically. It is assigned to each host by a network administrator based on the local network that the host is connected to

The structure of an IPv4 Address

The structure of an IPv4 Address

Remember these IP Adresses come in two generations, the IPv4 Addresses and IPv6 Addresses. IPv4 was the first generation to be used but has space limitation since only 3.4 billion addresses are available for allocation against the expected 50 billion devices to be live on the Internet by 2020. The IPv4 limitations eventually led to the current transition to IPv6 networks.

An example of an IPv4 network will appear on your device’s Internet settings in decimal format like while the IPv6 is designed in hexadecimal format like 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

The structure of an IPv6 Address

The structure of an IPv6 Address

Both the physical MAC and logical IP addresses are required for a computer to communicate on a hierarchical network, just like both the name and address of a person are required to send a letter.

A source device will send a packet based on an IP address. One of the most common ways a source device determines the IP address of a destination device is through Domain Name Service (DNS), in which an IP address is associated to a domain name. For example, www.cisco.com is equal to This IP address will get the packet to the network location of the destination device. It is this IP address that routers will use to determine the best path to reach a destination. So, in short, IP addressing determines the end-to-end behavior of an IP packet.

However, along each link in a path, an IP packet is encapsulated in a frame specific to the particular data link technology associated with that link, such as Ethernet. End devices on an Ethernet network do not accept and process frames based on IP addresses, rather, a frame is accepted and processed based on MAC addresses.

On Ethernet networks, MAC addresses are used to identify, at a lower level, the source and destination hosts. When a host on an Ethernet network communicates, it sends frames containing its own MAC address as the source and the MAC address of the intended recipient as the destination. All hosts that receive the frame will read the destination MAC address. If the destination MAC address matches the MAC address configured on the host NIC, only then will the host process the message.

To be continued on the next #TechExchange, stay tuned!!

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