Internet users who explore the concept of IP addresses, and check what their IP address is, will often find that it actually changes. You can check your public or external IP address (eg. 77.121.45.67) on one of those “what is my IP” lookup tools online, and find that it doesn’t stay the same and often changes.

Also, checking the local IP on your device’s Network/Wi-Fi settings (eg. 192.168.0.3), you’ll often find that changes as well. You might check back a few weeks later, and all of a sudden, it’s 192.168.0.11. Why is this? Why do IP addresses change?

To answer this requires defining and analyzing public and local IP addresses separately, since they both change for specific reasons. But here is a summary answer:

Your public IP address will change whenever there is a significant change or break in network conditions, such as changing routers, networks or providers, or factory resetting your router. Your local IP changes at set intervals determined by the router’s DHCP Lease Time, often set at 7 days.

The way that public IP addresses work means it is very hard to get them to stay the same permanently, whilst local IP address actually change by default, although it is possible to over-ride these settings if you’d rather it didn’t change.

Let’s look at all the reasons why public and private IPs change, plus ways to fix them in place if you prefer.

Public vs Private/Local IP Addresses

To thoroughly answer this question, we need to know which IP address we are talking about, since under the still predominant IPv4 addressing scheme, there are public/external AND private/local IP addresses. We’ll cover why both types changes in this article, but first we’ll explain why this differentiation exists.

Basically, because there aren’t enough unique public IPv4 addresses (that x.x.x.x format eg. 72.116.54.221) to cover every device on the planet, these public IP addresses are instead issued to routers/households rather than devices. Then Network Address Translation or NAT on the router splits these public IPs into a private IP address range for each network (that other common IP address range like 192.168.0.x that you’ve also probably seen).

See the diagram below for a good demonstration of how NAT splits public IP to private IP addresses:

NAT type resolves the issue of there not being enough unique IPv4 addresses in the world by converting a a public IP address (82.10.250.19 – issued by the ISP) into a private IP address and range (192.168.0.1-254) so it can then dish out the private (local network) IP addresses you see in the image to each device on the home network. The last digit changes for the local IP for each device on that network.

Now we’ve differentiated between public and private/local IP addresses, we can look in turn at why each of these types of IP can change, plus how to stop them from doing so.

Why Does Your Public IP Address Change?

As demonstrated above, public IP addresses are actually assigned or allocated to internet service providers or ISPs in the first instance, who then dish these public IPs out to their own customers as and when needed (remember, they are assigned to routers/households/networks, not individual devices, because there aren’t enough of them).

You can check your current public IP by using any of those free lookup tools online, such as:

• The whatismyipaddress.com IP lookup tool
• The whatismyip.com lookup tool
• The iplocation.net tool
• NordVPN’s IP address lookup tool

Something like this should display, giving your router’s public IP, ISP and approximate location:

 

Public IP addresses will change because there is a sufficiently large change in the network conditions that the ISP will be able to remotely detect it, most notably a break in the network or a change in hardware.

Examples of this include:

• Unplugging the router and plugging it back in (or power outages)
• Factory resetting the router
• Changing the router.
• ISP initiated maintenance resets (where the router seems to reset itself randomly).

If any of these things happen, your ISP will usually detect there has been a break or interruption in the network, and will therefore issue your router with a new public IP address from it’s allocated pool once it comes back online.

Public IP addresses are also unique, and convey unique information, such as the ISP and approximate location of the user. Therefore when any of these factors change, the public IP must also necessarily change, examples being:

• Connecting to a different router/network/Wi-Fi.
• Moving house
• Changing internet providers.
• Using a VPN software to forcibly change your IP and location.

See our article covering all these instances of when your public IP changes in more detail.

Therefore, whenever you’ve noticed your public IP address has changed, using one of those “what is my IP” lookup tools, it’s because something’s changed on your network which has broken the connection to the wider internet and led to your ISP issuing a new IP, or you’ve simply changed providers/location/hardware.

We have a section below on how to try and make your public IP more stable, but it’s virtually inevitable it will have to change at some point, even if just when moving house or changing providers, which we pretty much all do at some point.

Why Does Your Private/Local IP Address Change?

Now let’s turn to the private or local IP addresses issued to individual devices on a network. These are the common ones you’ll have seen within your device’s settings that run along a range, with the last digit changing for each device on the network. Some common ranges are:

• 192.168.0.1-254
• 192.168.1.1-254
• 10.0.0.1-254
• Other local IP ranges exist depending on the router.

Each device on the network just has a unique last digit in it’s local IP, like in the home network diagram above.

You can find a device’s current local IP address from it’s Network/Wi-Fi/Internet settings, or under Device Info/Status for phones. See our guide on devices for more on finding private IP addresses.

But why do these IP addresses also change? You’ll often find this even checking your device’s local IP from one week to the next, it might be mostly similar, but the last digit keeps changing. For example, your PC might have had 192.168.0.3 last week, but when you check again this week, it’s changed to 192.168.0.10. Why does this happen?

This is down to the Dynamic Host Configuration Protocol or DHCP settings on your router, which will by default keep swapping out and changing IP addresses of all connected devices at set intervals determined by the router’s DHCP Lease Time. This is the time interval that a router will “loan” or “lease” a local IP address to a device on the network for, before changing it.

When a device first shows up and connect to a router, it gets given an available local IP not in use by another device on the network. Then it’s like after a device has been connected to the router for this lease time (it’s often set at 168 hours or 7 days), the router says “OK, you’ve had that IP address long enough, I’m taking it back and here’s a new one”. And so the cycle begins again for the next X number of hours or days,  before the router switches out the IP address again for another one, and so it continues.

And as long as DHCP is enabled and not over-ridden by setting a static IP (see below), this will happen for all devices that connect to the router – their local IP addresses will change at quite regular intervals determined by the DHCP Lease Time, although it’s usually just the last digit changing.

With regards to WHY routers are automatically configured to keep swapping out and changing IP addresses of devices in this way, it’s basically to account for the fact the devices are always disconnecting/reconnecting from routers, and new devices are also being introduced. In other words, networks are always changing over time in terms of connected devices; therefore there has to be a dynamic, revolving system to assign IP addresses to newly connecting devices in a way that avoids two devices being issued to same local IP address on a network (IP conflicts).

If a device gets disconnected from a router, it can reconnect, but will likely be issued with a different local IP than before, as DHCP assignment is dynamic and constantly evolving, a bit like the networking equivalent of musical chairs.

DHCP Lease Time Explained

 

It is possible to manually alter the DHCP Lease Time on your router to make it longer or shorter if you desire. It’s noted in minutes or hours on some routers, so here are some markers:

• 1 week = 168 hours
• 1 week = 10,080 minutes

How To Stop Your Public IP Address Changing

Because there are so many different factors which can cause a public/external IP address to change, it’s quite hard to keep stop them from changing permanently.

However, you’ve got two main options to try and lock it in place:

Option #1 – Rent a Fixed Public IP – Some internet providers (not all though), do offer a service where you can rent a static/fixed public IP address from them for an extra monthly fee. Once activated, this should mean your router should keep the same public IP address as long as you stay with that ISP and don’t change any other major factors, like new ISP/moving home etc. Contact your provider to inquire about this, but it’s not always offered, and will cost extra when it is.

Option #2 – Use A VPN (Same server location or Dedicated IP) – This needs a careful explanation, as a VPN can’t always allow you to keep exactly the same public IP address, but will allow you to keep the same general IP location (in other words, while your public IP may change very slightly, as long as you select the same server location, you’ll always appear to at least be located in the exact same town/city).

But to be precise, even if you select the same server location from the VPN every time (eg. Houston, Texas), you won’t always get the same public IP address (it will vary slightly). But you WILL always appear to be based in that location, if that’s good enough for you. Also, like ISPs, some VPN providers do allow you to rent fixed public IP addresses, but it costs extra on top of a normal subscription. Check out real Premium, well known, longstanding providers like NordVPN for these services (look for a Dedicated IP feature)

These are your two main options for fixing your public IP in place, but in reality, it’s quite difficult and sooner or later, something usually changes or you move location in a way that means it must change.

How To Stop Your Local IP Address From Changing

If you’d rather your private or local IP didn’t change, this is actually easier to sort from within your router settings, since DHCP is a only default setting and can actually be manually over-ridden by the user.

You just need to log in to the router settings, and from there you can at least lengthen the DHCP Lease Time if this is good enough, or you can reserve a static IP for a device on the router, which fixes the local IP in place for that device and stops it from changing.

All router interfaces vary, but here’s a general process for reserving an IP on a router:

• Make a note of the current IP address and MAC address of your device. You can usually find this under the Network/Internet/Wi-Fi settings of the device, or under Device Info/Status for phones and tablets.
• Log in to your router. This usually means typing in a specific IP address into a browser address bar; it is often 192.168.0.1, 192.168.1.1 or 192.168.1.254 or may be something different. If you don’t know it, it will be on the back of your router somewhere along with the login password.
• Enter the admin/password – check the back of the router if don’t know them. See here for help with this if stuck.
• Once logged in, go to “Advanced Settings” or something similar.
• Select “LAN Setup/Settings” or something similar.
• Select “Address Reservation”, “DHCP Reservation/Server” or similar. Click “Add” to add a new static IP address.
• Input an IP address you want the device to have. The field is usually filled out as 192.168.0.x or 192.168.1.x or 10.0.0.x, with x being the custom number you put in to uniquely identify your device. This can be anything from 1 to 254 (sometimes the range is different as well, like 10.0.0.1-254); it is usually best to pick something in the middle like 100. You can put in the IP your device currently has if you noted it down.
• Add the MAC address also as noted down.
• Give the device a name (eg. Mike’s PC).
• Add the IP address, save settings and reboot the router.
• Reconfigure the internet connection on your device using the Easy/Automatic/Default settings to ensure ALL settings are set to default or automatic as the router is now handling IP addresses. Don’t set anything manually using this method, as your router is handling all that now. Just pick Easy/Auto Setup.

See our full article on locking your IP address in place for more detailed help, including videos and screenshots.

This is a good way of over-riding DHCP settings and lease times, and just locking a device’s local IP down permanently if you prefer to not have it change.

However, be aware that any major reset or change to the network can wipe any static IP settings on the router, and revert it back to DHCP settings, such as:

• Factory resetting router
• Unplugging router for a prolonged time (or power cuts)
• ISP maintenance resets
• New router.

Any of these factors change, you’ll have to re-do the static IP.