WiFi keeps disconnecting: why devices drop off

Telling two similar symptoms apart

“WiFi cuts out” can be two very different things, and confusing them means you fix nothing:

• The connection drops: the device stays attached to the network but loses its internet access. The usual cause is on the ISP side or is DHCP.
• It disconnects from WiFi: the device drops off and leaves the network, often every few minutes. The usual cause is signal or power saving.

The difference is easy to observe: on the router, a device that disconnects from WiFi disappears from the list; one that loses internet access stays listed with its IP.

Cause 1: there is only a 5 GHz network (common in IoT)

Most IoT devices (ESP32, ESP8266, Zigbee sensors with a WiFi coordinator, cheap cameras) are 2.4 GHz only. If your router broadcasts a single network name in 5 GHz, none of them can see it.

A very characteristic symptom: devices connect when you restart the router and then drop off, because the router assigns them an incompatible band.

Fix: enable the 2.4 GHz band with its own name and let IoT devices use it. See 2.4 GHz or 5 GHz.

Cause 2: WPA3 only

Older IoT devices don’t support WPA3. With WPA3 enabled they don’t connect; with WPA2 they do. If you changed the router security settings and a week later the sensors stopped responding, this is the cause.

Fix: enable WPA2/WPA3 mixed mode, which lets both kinds of client in. The details are in WiFi password, WPA3 and WPS.

Cause 3: 2.4 GHz interference and a congested channel

The most frequent cause. In 2.4 GHz there are only three clean channels (1, 6 and 11) and in a dense building there are dozens of networks. When the signal-to-noise ratio drops, the device disconnects to save battery and is then forced to reconnect.

Check: see whether the disconnections coincide with the times you use the induction hob, the microwave or the robot vacuum. Also compare what happens on 5 GHz.

Fix: fix the channel to 1, 6 or 11 and separate the bands. If the problem is only on 2.4 GHz, that’s almost always what fixes it.

Cause 4: DHCP problems (it isn’t always the lease)

This case confuses a lot of people because the symptom doesn’t look like WiFi. It’s worth clarifying the mechanism: when the lease expires, the router does not withdraw the IP address on its own. The client requests a renewal well beforehand (at the halfway point of the lease) and, if it gets it, it keeps the same IP address without dropping anything. That’s why a short lease, on its own, does not cause dropouts.

The mechanism is the one described in RFC 2131: the server leases an address for a given time and the client renews it before it expires.

What does cause dropouts:

• The device doesn’t manage to renew in time. This is the typical case: the device was asleep, woke up past the renewal point and doesn’t yet know which gateway to use. It recovers the connection within seconds, but you notice.
• The address pool has run out. With many devices, or with very long leases, the router runs out of free IPs and hands out duplicate addresses or rejects clients.

Characteristic symptom: a dropout every few hours, or on a regular schedule, with automatic recovery and no action needed.

Check: review the router logs and look at the size of the DHCP pool compared with the number of devices. If the dropouts coincide with the renewal and affect one specific device, that’s almost certainly the device.

Fix: raise the lease time to 720 or 1440 minutes and enlarge the address pool. Both are free. If the problem is a device that goes to sleep, the solution is to turn off its power saving (cause 5).

Cause 5: device power saving

IoT devices and smartphones save battery by switching the WiFi radio off when they aren’t using it. On a network with a good signal you don’t notice; with the signal at the limit the device has no margin left.

Check: see whether the dropouts affect a single device or the whole house.

Fix: if it’s an ESP32 or ESP8266, disable radio power saving in the ESPHome configuration with power_save_mode: none, and add a fallback network. If it’s a phone, it’s usually fixed by looking for the network again.

Cause 6: router out of resources

A router that is already stretched with few connected clients starts losing connections at thirty, because it runs out of memory or forwarding table entries.

Check: count the devices in the router’s list and look at the available memory if your device shows it.

Fix: make sure there are no ghost devices, or change equipment. The detail is in how many devices a router can handle.

Cause 7: roaming misconfigured on the mesh network

With several mesh nodes, an IoT device on the boundary between two nodes can switch access point constantly. Each switch is a micro-disconnection, and on an ESP32 it can mean a connection reset.

The solution isn’t technical but about placement: position the nodes so that the transit area doesn’t coincide with a room full of IoT devices, or lower the transmit power of the nodes if they overlap too much. See how to set up a mesh system step by step.

Cause 8: firmware with bugs

Old firmwares have known roaming and forwarding table bugs that show up as disconnections.

Check: look at the firmware version and compare it with the manufacturer’s.

Fix: update, and check first that you won’t lose the television service or the phone line if you use the ISP router.

Cause 9: the device’s power supply

An ESP32 powered by a weak USB charger reboots when the router transmits at higher power, because the radio signal draws current spikes. The symptom is disconnections when the light comes on or when the router reboots.

Fix: power the ESP32 from a stable supply, or fit a 1000 microfarad capacitor close to the power pin.

If it only drops on one device

If the rest of the house is fine and only one device drops, the problem is in that device, not in the network. The most common causes:

Five-minute diagnosis

1. Write down the exact time of three dropouts.
2. Look at the router’s device list at that moment: did it leave or is it still there?
3. Check whether the interval is regular: that points to DHCP.
4. Check the 2.4 GHz channel: are there more than four networks on your channel?
5. Test on 5 GHz with an affected device.
6. Update the firmware.

Quick checklist

1. 2.4 GHz channel on 1, 6 or 11.
2. DHCP lease of 720 minutes or more.
3. No duplicate IP reservations.
4. Radio power saving disabled on IoT devices.
5. Firmware updated.
6. Number of devices within the router’s limits.

Sources and next step

If the problem is performance rather than dropouts, read slow WiFi at home. To tell them apart, measure the signal with how to measure your home WiFi signal.

External sources

• RFC 2131: Dynamic Host Configuration Protocol — the standard that defines leasing, renewal and address pool behaviour.