In this guide, we’re going to explain the differences between static and dynamic IP addresses. Both types of Internet Protocol (IP) addresses have pros and cons, and we’ll help you to understand which one is best suited to your needs.
But first of all, here’s a bit of geeky humor to get started: “There’s no place like 127.0.0.1.” If you can get that joke, you might have a lot of this article understood already.
IP addresses have been around for almost 40 years. Since the first Internet protocol was used in ARPANET, which was a predecessor to the modern-day Internet. We’ve seen IP addresses using the Internet Protocol v4 (IPv4) become exhausted. And the creation of Internet Protocol v6 (IPv6) coming into its own in recent years.
IP networking is likely always going to be something IT Pros need to understand. However, the world is changing. The likelihood of our grandchildren needing to worry about subnets is unlikely, with the release of IPv6 and its massive amount of usable IP Addresses, which totals 340 trillion trillion trillion unique addresses. That is a much more than the 4,294,967,296 that IPv4 provides.
The key thing here is to realize that with a traditional IPv4 network, IP address can be assigned to a host dynamically when it is added to your network. Otherwise, a host is assigned a persistent address through the configuration of the hardware or software on the network.
A static IP address is also known as a persistent IP address. Often, we assign this static IP address to the host and the device will use it until the device is removed from the network. Otherwise, when the network undergoes some changes, the device will need to have a new static IP address assigned to it.
Another reason we may have a static IP address is if we want to have one assigned to our business or home network from our Internet Service Provider (ISP). By having a static IP, we can enable Domain Naming System (DNS) to point external services, such as websites or line of business applications, to the address without worrying about it having to change.
Some key reasons why static IP addresses are useful are because of the following:
These are all positives, but what about the disadvantages of having a static IP address? Here are some examples:
Dynamic IP addresses are assigned to the host system. The address can change, or it could ultimately become sticky, which we will talk about in a moment.
Because of the limitations of IPv4 addresses outlined above, IT pros need to adapt to how their internal networks operate. For example, if we were to run a business or a home network, our Internet provider could give us a single IP or a small range of IP addresses, which would be used sparingly. Internally, we could have hundreds, if not thousands of IP addresses being assigned to hosts.
IP addresses are assigned dynamically using something called Dynamic Host Configuration Protocol, or DHCP. The perks of using a DHCP server is that it removes the requirement of manually assigning a new IP address to every single item which joins your network. It also ensures that the IP address assigned to everything on your network is only assigned for a period.
For example, your son’s friend who stopped off last week and joined their phone to your home’s broadband network was assigned an IP address, and for a period that IP address is allocated to the phone. However, after a determined period, that IP address that was assigned to the phone will be reallocated to the DHCP pool of IP addresses, and it can be reassigned to the next host that requires it. By default, with most modern equipment, dynamic IP configuration is the norm.
“Sticky” IP addresses are an informal way of saying that a dynamic IP address very rarely changes. We may have a piece of equipment that is always on our home network such as a doorbell, a CCTV camera, or any smart item that never leaves the confines of your home network – this device will be assigned a dynamic IP address.
However, when it comes to renewing the address, the host and the DHCP server will likely agree on the same IP address. In doing so, the IP address will become “sticky,” as it never changes unless something else does.
It’s a bit like the first law of motion with physics – An object will remain at rest or in a uniform state of motion unless that state is changed by an external force. A dynamic IP address works the same: It will remain unless it is impacted by an external force.
The rule of thumb is that anything can change. However, it’s unlikely that you would change a static IP address unless there is a good technical reason to do so.
A common reason you might want to change a static IP address is your constant level of attacks to an external static IP address. If you’ve made the decision that moving from one IP address to another is going to occur, yes, this is technically possible.
However, it does mean that you will need to update your DNS records, which will affect any items hard-wired to use the old IP address – it’s not a small undertaking.
Dynamic IP addresses are meant to change. As the pool of IP addresses is used by the hosts that require them, when these dynamic IP addresses are no longer needed, they are returned to the pool.
You can think of this as a public library – when you need to add yourself to your network you ‘check out’ the IP address book. When you’re finished, you return it to the ‘librarian’ who puts the IP address book back on the shelf.
You should use a static IP address when you consistently want to get back to the same location. An example of this would be a server being hosted on my local network. This could be something like a website, intranet, email server – most servers are assigned a static IP address.
Using static IP addresses outside your local network can raise a security risk as they make you easier to find. If you are always using the same address and someone wanted to find you, it’s easier with the same address vs. someone who’s changing it regularly.
If you have a static IP address, someone with the right tools could also find out exactly where you live. There are websites dedicated to doing a reverse look-up from your IP address and then applying this to your IP location. Therefore, businesses can get roughly close to where you are located and apply adverts to things that are within proximity of where you are.
Dynamic IP addresses are useful when we want to assign an IP address without having to worry about the administrative overhead of the assignment of the address. Traditionally we would allow the DHCP servers or network routers to handle the allocation for us. We would use a dynamic IP address in places where we don’t require a static IP to be applied.
An IP address pool is a sequential range of IP addresses within your network. For complex networks, we can find that there are multiple pool configurations using multiple IP address pools. With a DHCP server, we would apply an address from a single pool or from multiple pools and the server infrastructure will apply it.
Most IP address pools utilize something called the Least Recently Used (LRU) method when assigning an address. This means that IP addresses are assigned to a queue and the IP address is released when it reaches the end of the queue.
This is pretty much everything you need to know about static and dynamic IP addresses, and we hope this guide helped you to understand the best use cases for each of them. If you need more information about IP addresses, DNS, and other core Internet technologies, make sure to check out our Networking category on Petri.