We already know the irritating effects of power cuts on computer and internet users – we can lose work, downloads and the great film we were watching, but what about router settings and IP addresses when the power goes out? Does the IP address of your network (public IP) and device (local IP) change whenever there is a power outage?

We need to differentiate between the two types of IP address, but the basic answer is yes:

A power cut generates a break in the network connection, meaning that your ISP will issue your router with a new public IP once it comes back online. The local IP addresses of devices on the network will also change as the router must re-do all the DHCP assignment once the power comes back on.

Therefore, yes, power outages are a big disruption to home networks, and they do reset everything, including IP addresses. If you are a gamer and have a static IP set, this will also be lost and you’ll have to re-do it on the router, but we’ll show you how.

What Happens To Your Public IP After A Power Outage?

Public IP addresses are those outer facing ones that websites and those “IP lookup” tools detect when you visit them (eg. 77.123.45.223). They are uniquely assigned to internet providers (ISPs), who then assign them to customer’s routers dynamically and randomly.

See here for more on public vs private/local IP addresses, with network diagrams and videos. We’ll keep the theory light in this post.

If your network just functions normally day to day without interruption, then it’ll be fine. But any kind of major change or disruption to the network or connection, then your ISP will detect that the connection to your router has been lost/broken, and issue a new public IP address to it once it comes back online.

And a power cut represents one of those disruptions. Your IP address will change once you bring your router back online after a power cut, as your ISP will dynamically allocate a fresh public IP to your router once the service is restored.

Therefore if you check your public IP with one of those “what is my IP” lookup tools, you will find it is different after the power cut than before.

The same thing happen when you break or alter the network in any other way, like factory resetting your router, changing your router, changing your ISP, moving home. Any time a major factor or “link in the chain” of the network from your home to the wider internet either breaks or changes, your public IP address will tend to change.

Will Your Private/Local IP Also Change After A Power Cut?

What about the private/local IP addresses assigned to individual devices on a network by the router? These are the ones commonly along the range of 192.168.x.x, with the last digit changing for each device on the network. You can find the current local IP of you device within it’s Internet/Network/Wi-Fi/Device Status menu.

These local IP address actually change at set intervals anyway if using the default DHCP settings of the router, which automatically hands out local IP addresses (eg. 192.168.0.1-254) to any device that shows up on the network, and swaps them out at set intervals determined by the router’s DHCP Lease Time (often 7 days).

But a power cut pre-empts and cuts short this process, pun intended. Because a complete cutting of the power effectively resets the router, meaning that once it comes back online, it’s got to re-do all it’s DHCP assignment, dishing out brand new local IP addresses to all the devices on the local network again.

Therefore, all the local IP addresses of devices will also change once the router restarts after a power outage, but they won’t drastically change. It’s really just going to be the last digit that changes as the router shuffles things around a bit. For example, before the power cut, your games console might have had 192.168.0.3, but after the power comes back on, it’s now been assigned 192.168.0.21 by the router.

Speaking of games consoles though, if you were using a static IP for any device before, this will be lost in a power cut as with all other custom router settings, and you’ll have to re-do it (see section further below for steps).

Will Power Cuts Always Have This Effect?

It is true that there are differing types and severity of power cuts. Sometimes you might just have very minor or momentary outages, where the lights flicker or go out, but only for a fraction of a second before coming back on.

I’d like to test this out, but I think in these cases, you might get away with it, and the network conditions (including the public and local IP address) might be maintained as they were with only very brief outages.

Anything more than than though, where the power clearly goes fully out and is off for several seconds or more, you can safely assume your router is going to be fully reset when coming back online, and it’s IP address will have changed. Certainly if you get that “no internet” sign on your device, you know the connection has been broken, and therefore your IP address is going to change once the service comes back on.

Re-Configuring a Static IP After A Power Cut

If you have reserved a fixed or static local IP address for a device on the network to stop it from changing, this will be lost during the power cut, and you’ll have to re-do it once your router come back online.

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.
• 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.

Reserving IP Address On Router (Quick General Guide)

 

See our full article on locking your IP address in place for a device for more detailed help.

What About Unplugging Your Router?

This is a closely related scenario – what if you just unplug your router from the wall, and then plug it back in again? Is that enough to change the IP address? Again, the answer is yes, because it’s basically the same effect as a power cut, but just applied to your router alone.

Fully unplugging your router is enough of a break in the connection for your ISP to detect it, and therefore it will issue your router with a new public IP address when you plug it back in.

Therefore, it works much the same as a factory reset, in that it does break the network enough for a fresh IP to be issued (soft resets where you push the reset button usually don’t though).