Static vs. dynamic IP addresses: What's the difference and why you need to know

An IP address is a way for every device on a network to be seen. Without IP addresses it would be impossible for those devices to be located.

Consider an IP address for your computer like the street address for your house. Without a street address, it would be challenging (if not impossible) for others to find you. Unlike a computer’s IP address, however, the only time your home address changes is when you move. Your devices, on the other hand, can have their IP addresses changed (depending on the device type).

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There are two main types of IP addresses —  static and dynamic. I’ll explain them both — and why you would choose one over the other.

Static IP addresses

Simply put, a static IP address does not automatically change. Once you set a static IP address, it remains until you manually change it. (A static IP address is the one most analogous to your home address.)

But why would you choose a static IP address? Most often, you won’t. Static IP addresses are generally assigned for machines where the IP address needs to remain the same. For example, I have a network share on my desktop computer (running Pop!_OS Linux). If I used a dynamic IP address on that machine, the IP address could  — and eventually would — change on me. If I’m on a different machine within my home network, and I go to save a file to that share, I’d be prevented from doing so because the IP address is no longer the same. I’d have to go to my desktop, locate the IP address (such as with the command ip -a), and then reconnect the other machine to the share. 

When that desktop machine is configured with a static IP address, there’s no need to worry about that IP address changing.

But there’s an inherent problem with this. Let’s say you assign the IP address 192.168.1.100 to your desktop and it works great. But then, at some point, your router assigns that same address to another machine (because the router doesn’t know you’ve already used that address). Should that happen, you’d wind up with IP address conflicts — and problems could occur. Say you’re on your laptop and need to mount the network share. If your router has assigned that same IP address to another machine, your laptop might not know which machine to use and would fail to mount the share.

Here’s how to avoid that problem: If you need to assign static IP addresses to machines on your home network, configure your router to assign dynamic IP addresses only within a specific range. For instance, you might set the dynamic range between 192.168.1.1 and 192.168.1.99. That way you can use IP addresses 192.168.1.100 and up for static usage.

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How you assign a static IP address will vary, depending on your operating system. Generally speaking, you go to your network settings tool, locate the connection to be configured (such as wired or Wi-Fi), open the options for that device, and configure the following details:

• IP address
• Gateway (usually the address of your router or modem)
• DNS (third-party services, such as Cloudflare’s 1.1.1.1 and 1.0.0.1)

Dynamic IP addresses

Dynamic IP addresses are assigned to the devices on your network by your router and DHCP (Dynamic Host Configuration Protocol). They are called dynamic because they can change. The change is defined by what’s called a lease and the period of the lease varies, depending on your router. Lease periods can be anywhere from one week to several months. Here’s how it works:

1. A machine requests a new lease for an IP address.
2. The address is assigned by the router.
3. Halfway through the DHCP lease period, the machine attempts to renew the lease (so it can keep the same IP address).
4. If the renewal fails, the machine will be given a new IP address.

Many routers allow you to configure the lease periods but most users should leave the default settings for this. 

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For the most part, dynamic IP addresses are easier to use because they ensure you won’t have to worry about IP address conflicts. Most devices default to dynamic IP address assignment, so you don’t have to configure anything (beyond the possible selection of the network you want to use).

As noted earlier, the only time you’d want to opt for a static IP address is if you have a machine on your network that serves a specific purpose and a change in IP address could disrupt that purpose. Even then, the machine most often will successfully renew its DHCP lease, so there shouldn’t be any problems. However, if you do encounter a problem, consider going the static route. Just make sure you can configure your router’s dynamic IP address range to avoid IP conflicts.

And that’s the gist of static and dynamic IP addresses. Chances are pretty good that you’ll never have to deal with any of this, but on the occasion that you do, you now understand the difference.