MAC and IP Addresses – Quick Summary

Last Updated on January 19, 2024 by theadmin

What are Mac and IP Addresses?

The focus of this site, is the use of IP addresses, particularly residential ones, to stay anonymous online.  Whether for safety, security or just to enable multiple digital identities having just one easily tracked IP addresses linked and logged by your ISP doesn’t quite hack it for many of us.   However the term IP address is used to provide and sell sometimes really expensive services, so it’s good to know exactly what it means before you invest money in IP related services.

The Two Important Addresses that the Internet Needs

When dealing with networking technologies there are two important addresses, without which much of our modern world simply wouldn’t work.  We have physical layer MAC addresses and of course, IP addresses.  Here’s a reminder of the acronyms involved –

  • IP Address –  Internet Protocol Address, a logical network address.
  • MAC Address – Media Access Control Address, an address applied to a physical device.

Both these addresses are vital for network communication yet they exist and operate at completely different levels.  If you take a network analyser and search the headers of IP packets looking for a MAC address of a device, you won’t find a thing.   This is because a MAC address doesn’t mean anything to the Internet protocol which exclusively use logical addresses.   They are not part of the protocol and so are not even recognized.

The physical MAC address is commonly assigned to the network card of a device, which is typically an ethernet card (although other topologies do exist).   The physical MAC address is the method  which the card interfaces with the digital network.  Your network card doesn’t know anything about how the internet protocol or how IP addresses are assigned. Clearly there is an issue here – two addresses which don’t understand each others existence but have to communicate.

Do You Know Your IP Address?

Most people don’t know any of the IP addresses they use. For a start, the internet facing one or external IP addresses of your connection probably changes quite often. This is because the worldwide IP address space, the table of available addresses is both limited and carefully managed.   When you connect to the internet, then you will be allocated an Instagram IP address but it’s not yours permanently.  The address is loaned or leased to you if your at home then it’s probably assigned by your Internet service provider.  Therefore you will connect to the internet using an address from a residential range.

Normally the allocation of IP addresses is on a lease arrangement usually facilitated by an application known as DHCP (Dynamic Host Control Protocol).  This is a protocol which allows the temporary, dynamic assignment of IP address numbers.   In the early days of networking this address assignment involved centrally managing and assigning static addresses.  DHCP makes this much simpler allowing any host to be allocated an IP address automatically for a given amount of time.

If you want to learn more about DHCP, then this video is a pretty comprehensive introduction.

The governing body of the internet and the group responsible for the allocation of IP address is the Internet Address Numbers Authority (IANA). They have allocated various ranges for different uses including blocks of addresses which can be used for internal address. These include the ranges 192.168 and 172.16 which is why you’ll usually find any network enabled device like a router or modem will be pre-allocated an IP address from this range. The crucial distinction of the private address range is that they should only be used for hosts on a particular network. The traffic should not leave the site’s external gateway for the very good reason that these addresses are used globally and are not unique.

You Definitely Won’t Know Your MAC Address

Of course, somewhere, someone will probably have memorized their MAC address but it’s certainly no easy feat. There are several reasons including there is no real requirement for most of us to remember it. However the most obvious reason is that a MAC address is a 48 bit number which is completely unmemorable to a human brain. You’d have to make a real effort to memorize this number and it would have no real practical use.

This is because as we mentioned earlier there is a requirement for something to facilitate communications between IP and MAC addresses which does it for us automatically.  This ifgs another useful application called the Address Resolution Protocol (ARP) which enables the resolution of physical MAC address to logical IP addresses. Although it’s name is slightly misleading as it’s not really an Internet protocol application rather the process of sending an Ethernet frame to all systems on the same network.

This is how ARP works,  by broadcasting a request to all machines on the same network.  Any device which hears this broadcast will reply with it’s own MAC address. In addition, every machine will cache previous addresses which it also can resolve.  You can see it working on any computer – just go to the command prompt on a windows machine for example and use the arp command –

Here’s the output from my machine, a list of IP addresses and their associated MAC addresses.   You can see a range of internal IP address and some from the range 224.0 which is reserved for IP multi casting.  Remember though the communication is taking place between MAC addresses and not IP addresses.

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