Network Problems After a Power Outage

The pattern repeats everywhere: power out for an hour, then back. The router lights look normal, phones join the Wi-Fi, but not a single page loads. What makes it confusing is that everything looks fine.

Nearly every case resolves through the same sequence of checks, and the sequence matters.

The most common cause: startup order

Check this first because it's the most frequent and the easiest to fix. Two devices power up together when electricity returns: the modem or ONT that connects to the provider, and the router that shares the connection (the difference is in modem, router, and ONT).

The modem takes longer to be ready, sometimes one to three minutes, because it has to renegotiate its link to the provider's network. The router boots faster, immediately looks upstream, finds nothing, and stops trying. After that it keeps broadcasting Wi-Fi quite happily, with no path out.

The fix: unplug the router, wait until the modem or ONT light is steady, then power the router. If the indicators aren't clear, wait two minutes. What the lights mean is in router indicator lights.

If the ONT light is red or blinking

If after waiting the ONT stays red, amber, or blinks on LOS or PON, the problem isn't inside the house. Possibilities:

• A fault on the provider's side, especially after a wide outage. Their street equipment has also just restarted, and sometimes needs time.
• The fibre connector shifted while the device was powered down. Carefully unplug and refit the yellow connector, and clean the tip if dusty. How to, in caring for fibre at home.
• The ONT was damaged by a surge. The costliest outcome, and most common after an outage that recovers in stages, since voltage swings several times before settling.

Here, restarting repeatedly won't help. Call the provider and state the light colour, because that's the first thing they'll ask.

Devices missing from the network

The second classic symptom: internet works fine, but the printer isn't found, the camera won't open, or network storage doesn't appear.

Nothing is broken. The router reassigns local addresses from scratch at boot, and the address the printer held can go to another device that happened to start first. The app on your phone or computer is still looking for the old one. Explained in local IPs, DHCP, and conflicts, with the symptom in devices not visible on the network.

Temporary fix: restart the missing device. Permanent fix: give each one a DHCP reservation on the router, a fixed address always issued to it. Set once, and this complaint never returns after future outages.

A router with the wrong clock

A subtler symptom, often unrecognised. Routers have no clock battery, so after an outage they start from the wrong time until they can sync over the internet. While the clock is wrong:

• Wi-Fi on/off schedules run at the wrong times (scheduling Wi-Fi).
• Time-based parental controls don't apply as intended (parental controls on the router).
• Some sites fail with invalid certificate warnings, because certificates are checked against the wrong date. The same happens on phones and computers whose clocks have drifted.

It usually corrects itself within minutes of internet returning. If not, check the router's time settings and confirm the time zone.

Cameras and smart devices that don't come back

Wi-Fi cameras and smart devices are the worst at waking properly. Many try to connect a few times then give up, exactly like a router that failed its upstream search. If a camera hasn't returned after five minutes, unplug it and power it again once the router is genuinely ready. Further care in CCTV camera security and smart home device security.

If this happens every time

Outages can't be prevented, but their effects can. If your home or business loses power regularly, two steps remove almost every complaint above:

• A small UPS for the modem and router. Both draw very little, so a cheap UPS can hold one to two hours. Nothing ever powers off, so there's no wrong startup order, no addresses moving, and no clock drift. Options in a UPS for your router.
• DHCP reservations for every fixed device: printer, cameras, network storage, till. One-time work, permanent effect.

If your router restarts by itself outside of outages, that's a different problem, covered in routers that restart on their own.

Frequently asked questions