Quick answer
An IP address conflict occurs when two devices on the same network use the same IP address, most often due to a manually assigned address or a DHCP reservation error. The fix is to switch the conflicting device to automatic address assignment (DHCP) or assign a unique reservation on the router.
How to recognize the problem
- Message "Windows has detected an IP address conflict" or a similar warning
- Connection drops and returns intermittently, especially on one device
- Device cannot connect to the network even though Wi-Fi signal is strong
- Access to shared folders or printer works on only one computer
- Two devices with the same IP address appear on the network
Most common causes
Manually assigned IP address
Someone manually set an IP address on a device that is already in use or falls within the router's DHCP range. The router may assign that address to another device, causing a conflict.
DHCP reservation error
The router has the same IP address reserved for two different devices (for example, after replacing a network card). The router then assigns the same address to both.
Device with a static address
An older printer, NAS, or camera has a fixed IP address that matches the address DHCP assigned to a computer or another device's address.
Two DHCP servers on the network
A second router or device with DHCP server enabled hands out addresses from the same range, causing duplicates. This often happens when a second router is added as a network extension.
Step-by-step fix
- 1
Confirm that a conflict exists
On Windows, open
Command Promptand typeipconfig /allto see the current IP address and whether it was assigned via DHCP. If you see a conflict warning in events or notifications, the problem is confirmed. On macOS, openSystem Settings > Network > Wi-Fi > Detailsand check the IP address. - 2
Switch the device to automatic address assignment
On Windows:
Settings > Network & internet > Wi-Fi(or Ethernet) > click the network >IP assignment > Edit > Automatic (DHCP). On macOS:System Settings > Network > Wi-Fi > Details > TCP/IP > Configure IPv4 > Using DHCP. This is the safest solution because the router assigns a unique address. - 3
Restart the network adapter or device
On Windows, in
Command Prompt, typeipconfig /releasethenipconfig /renew. On macOS, turn Wi-Fi off and on. If that does not help, restart the computer or phone. - 4
Check DHCP reservations on the router
Log in to the router (the address is usually
192.168.1.1or192.168.0.1) and find the list of connected devices or DHCP reservations. Make sure no IP address is reserved for two devices. Remove duplicates. - 5
Find the device with a static address
If the conflict persists, disconnect devices one by one (printer, NAS, camera) and check whether the problem disappears. When you find it, change its IP address to a free one or switch it to DHCP.
- 6
Check that there is no second DHCP server
In a home or small office network, there should be only one DHCP server. A second router connected via LAN cable should have DHCP disabled or operate in access point mode. Check whether a device has accidentally enabled DHCP.
- 7
Clear the ARP cache and restart the network
On Windows, in
Command Prompt(as administrator), typearp -d *andipconfig /flushdns. Then restart the router and computer. This helps remove stale ARP and DNS entries. - 8
As a last resort, reset network settings or renew the DHCP lease
On Windows:
Settings > Network & internet > Advanced network settings > Network reset. This will erase all custom network settings, so note them down before resetting and reconfigure them afterward. On macOS:System Settings > Network > Wi-Fi > Details > TCP/IP > Renew DHCP Lease; this only renews the DHCP lease and does not reset all network settings.
If nothing helps
If the conflict recurs after all steps, check whether the problem is in the router itself (outdated firmware, DHCP bug). Update the router firmware according to the manufacturer's instructions or reset it to factory settings. Before a factory reset, back up the router configuration and note the internet and Wi-Fi details, because the reset will erase all settings. Then reconfigure the network. In a business environment, a conflict can also be caused by a virtual machine or VPN adapter using the same address range as the local network. In that case, the solution is to change the range in the VPN settings or disable unnecessary network adapters. If you have multiple access points, check that none is broadcasting DHCP. For diagnostics, you can use free tools such as Advanced IP Scanner, or the arp -a command to see IP and MAC addresses from the local ARP cache.
How to prevent it
- Use DHCP for all devices except servers and printers, for which you assign a reservation on the router.
- Create DHCP reservations on the router for devices that need a fixed address.
- Do not connect a second router via LAN cable unless its DHCP is disabled.
- Periodically check the list of connected devices on the router for duplicates.
When to call a professional
If you cannot access the router, do not know the password, or the conflict recurs after all steps, contact IT support. They can analyze the network, check DHCP, and safely change settings.
IT infrastructure maintenance · Servers, networks, backup, security and helpdeskFAQ
How do I know I have an IP address conflict?
Windows usually displays a notification "Windows has detected an IP address conflict" or shows a warning about a duplicate IP address in network connections. You can also check `Event Viewer` under Windows Logs > System, where an event with source `Tcpip` and a conflict description appears.
Is an IP address conflict dangerous?
It is not a security risk, but it causes connection drops and prevents normal network operation. Two devices with the same address cannot reliably communicate at the same time, leading to packet loss and instability.
Can I change the IP address on the router myself?
Yes, if you know the router administration password. Log in to the router, find the LAN or DHCP settings, and there you can change the range or add reservations. If you are not sure, it is better to leave it to an expert.