What DHCP does
DHCP (Dynamic Host Configuration Protocol) is the router feature that automatically gives each device on your network an IP address, along with other settings such as the gateway and DNS server. When it works, you never notice it. When it stops, devices may show messages like “Limited connectivity”, “No DHCP server found” or “Unable to obtain IP address”, or they may assign themselves an address that begins with 169.254, which typically means the device asked for an address and got no answer.
Work out where the failure is
- One device or all of them? If only one device fails, the cause is often on that device (a fixed IP setting, a network adapter problem or a driver). If every device fails, look at the router.
- Wi-Fi only, or Ethernet too? If Wi-Fi devices work but a computer on Ethernet does not, suspect the cable, the port, or that computer’s adapter.
- Does the router have internet? DHCP on your own router is separate from whether your provider connects you. A router can hand out local addresses with no internet behind it, which is covered in our article on what a wireless router can do without internet. Some setups also depend on the provider’s equipment handing the router an address, so a problem there can look similar.
Common causes
- A router that has been running a long time and needs a restart
- The router’s DHCP server being turned off, sometimes by accident
- An address pool that is full, for example when many devices connect or the pool is set too small
- Two devices acting as routers on one network, each running DHCP, which can conflict
- A device set to use a fixed (static) IP address that does not suit the network
- A faulty cable, port or network adapter
- A driver or software problem on the device
- A firmware bug on the router or a new modem that has not been registered with the provider
Fixes to try
1. Restart in the right order
Turn off the modem and router, wait about 30 seconds, turn on the modem and wait for its lights to settle, then turn on the router. Then restart the affected device.
2. Switch the device to automatic addressing
Check that the device is set to “Obtain an IP address automatically”. A leftover static setting from an old network is a common cause.
3. Renew the lease on a computer
On Windows, open Command Prompt and run:
ipconfig /release
ipconfig /renewThis asks the router for a new address. On Wi-Fi, you can also turn the adapter off and on, or run the Windows network troubleshooter. On phones, forgetting the network and reconnecting has a similar effect.
4. Check the router’s DHCP settings
Log in to the router’s admin page (commonly a local address such as 192.168.1.1 or 192.168.0.1, though yours may differ). Look for the DHCP or LAN settings and check that:
- The DHCP server is enabled.
- The address range is large enough for your devices.
- The lease time is reasonable (the default is usually fine).
If you cannot reach the admin page because your device has no address, connect a computer by Ethernet and set a temporary static address in the router’s range, or use a device that still works.
5. Look for a second DHCP server
If you have added a second router, an extender or a modem-router combination, only one device on the network should normally hand out addresses. If the second device is only meant to extend the network, put it in access point or bridge mode, or turn its DHCP off. Check its manual for the correct setting.
6. Update the firmware
Check for a router firmware update. Some owners have reported that updating firmware and then resetting the router helped when DHCP stopped working after a hardware change. If you use a reset, note that it erases your settings.
7. Test the hardware
Try a different Ethernet cable and a different router LAN port. Try another device on the same connection. If a single Windows computer fails everywhere, reset its network adapter or reinstall the adapter driver.
When nothing works
If several devices fail after a restart, settings check and firmware update, the router may be faulty. A factory reset is the last software step, and replacing the router is the next. If you have a router supplied by your provider, contact them. For broader dropout causes, see why a router keeps going out, and for brand-specific steps see Linksys not connecting to the internet or ASUS routers dropping the connection.