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The warning means Windows has detected that two devices appear to be using the same IPv4 address, or that a router or switch probe collided with Windows’ duplicate-address check while a DHCP lease was being offered. On a DHCP network, capture the current settings, release and renew the lease, then investigate the router if the warning returns. On a static setup, remove the overlapping address or reservation.
The steps below distinguish a one-time DHCP collision from a recurring infrastructure problem without disabling the checks that protect the network.
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What “Windows has detected an IP address conflict” means
An IPv4 address identifies a device on your local network. A conflict occurs when Windows receives evidence that another device is answering for the same address. Both devices may then lose internet or local-network access, show intermittent connectivity, or trigger the warning repeatedly.
Microsoft explains that a Windows DHCP client sends a gratuitous ARP request to perform client-side conflict detection before it finishes configuring the server-offered address. A router or managed switch can send its own ARP probe during that brief phase. That timing collision can activate the conflict path even when no second computer is intentionally configured with the same address. The alert therefore does not, by itself, prove malware or an intruder.
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“Windows DHCP clients that obtain an IP address use a gratuitous ARP request to perform a client-based conflict detection before completing configuration and using the server-offered IP address.” — Microsoft Learn
Do not solve the message by disabling duplicate-address detection. Microsoft warns that doing so can allow a genuine duplicate to remain hidden.
Before changing anything: capture the network state
Record the details first. They show whether the adapter is using DHCP, identify the address that collided, and give a router administrator enough information to trace the other device.
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problems- Open Command Prompt as administrator. In Windows 11 or 10, search for
Command Prompt, right-click it, and choose Run as administrator; approve the User Account Control prompt. - Run
ipconfig /all. - For the affected adapter, copy the adapter name, IPv4 Address, Subnet Mask, Default Gateway, DHCP Enabled state, DHCP Server, and Physical Address (the MAC address). Note whether the problem is on Wi-Fi, Ethernet, or both.
Keep this output until the issue is resolved. If the address begins with 169.254, Windows has assigned an automatic private address because it did not obtain a usable DHCP lease; that is a DHCP-communication problem rather than proof that another device owns the address.
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Fix a DHCP-managed adapter
Most home and small-office networks assign addresses automatically. In ipconfig /all, check that DHCP Enabled says Yes and that a DHCP server is listed.
- In the elevated Command Prompt, run
ipconfig /release. This sends DHCPRELEASE and discards the current IPv4 configuration, so the affected connection will briefly go offline. - Run
ipconfig /renew. Windows requests a new configuration from the DHCP server. - Run
ipconfig /allagain and confirm that the adapter has an IPv4 address, subnet mask, gateway, and DHCP server. Test a local device and then a website.
A single collision that disappears after renewal may have been a stale lease or a timing collision during address detection. If the same warning comes back, renewal has not corrected the underlying scope, reservation, or DHCP-server problem; continue with the infrastructure checks below.
Fix a manually assigned (static) address
Renewing a static address does not solve an overlap. A manually assigned address can conflict when it falls inside the router’s DHCP pool, matches another device’s static setting, or no longer matches a reservation.
- Open Settings and go to Network & internet > Advanced network settings > More network adapter options. (The wording can vary slightly by Windows release.)
- Right-click the affected Ethernet or Wi-Fi adapter, choose Properties, select Internet Protocol Version 4 (TCP/IPv4), and choose Properties.
- If the network is intended to use DHCP, select Obtain an IP address automatically and Obtain DNS server address automatically, then apply the change.
- If a static address is required, obtain a unique address from the network administrator. It must use the correct subnet mask and gateway and must be outside the router’s DHCP allocation range unless the administrator has created a matching reservation for that device.
- After changing the setting, run
ipconfig /alland test connectivity.
Do not guess a “free” address on a managed network. An address that looks unused now may belong to a sleeping laptop, printer, phone, virtual machine, or reserved device that will reconnect later.
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Reset the Windows networking stack when other symptoms point to corruption
If the conflict message appears alongside broken DNS resolution, failed connectivity after a lease change, or other TCP/IP errors, Microsoft’s manual reset sequence can rebuild the local networking components. It does not repair a duplicate DHCP reservation, so use it with the configuration checks rather than instead of them.
- Open an elevated Command Prompt.
- Run
netsh winsock reset. - Run
netsh int ip reset. - Run
ipconfig /release. - Run
ipconfig /renew. - Run
ipconfig /flushdns. - Restart Windows if prompted, then run
ipconfig /alland test the connection.
These commands reset Winsock, TCP/IP parameters, the DHCP lease, and the DNS resolver cache. They do not change the router’s address pool or reservations.
Investigate the router and DHCP service when the warning returns
Recurring conflicts usually require a look at the network infrastructure. Sign in to the router or DHCP server using its documented local administration address, or ask the network administrator to perform these checks.
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- Review the DHCP scope. Confirm the start and end of the allocation range and look for a range that overlaps manually assigned addresses.
- Check reservations. Search for duplicate reservations or two MAC addresses mapped to one IPv4 address. Correct the reservation and restart or renew the affected clients.
- Look for a second DHCP server. An old router, extender, virtual machine, Internet-connection-sharing host, or misconfigured access point can answer DHCP requests with a different pool. Only the intended DHCP service should be active on the LAN.
- Match the address to a device. Compare the conflicting IPv4 address and MAC address from
ipconfig /allwith the router’s client or lease list. Identify the second device before changing either configuration. - Check ARP or duplicate-address protection settings. On managed switches and routers, an ARP probe during Windows’ address-detection phase can create the warning. The administrator should correct the probing behavior or delay it; disabling duplicate-address detection on Windows merely hides evidence of a real conflict.
After a correction, clear or renew the affected leases according to the router’s documentation, then use ipconfig /renew on the client. Keep a note of which device owns each static address and reservation so the same overlap is not recreated during a later replacement.
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Use the symptom pattern to choose the next test
| Pattern | Most useful interpretation | Next action |
|---|---|---|
| One-time warning; renewal works | Stale lease or DHCP/ARP timing collision is possible | Monitor the connection and retain the captured lease details |
| Returns after every renewal | Overlapping scope, duplicate reservation, or second DHCP server | Inspect the router/DHCP service and identify the other MAC address |
| Only a static device is affected | Manual address overlaps a lease or another static assignment | Move it to a unique address or use a corrected reservation |
| Ethernet only | Cable, switch port, wired adapter, or wired DHCP path may be involved | Run the wired hardware isolation steps below |
| Wi-Fi only | Wireless router, access point, or its DHCP service is the first place to check | Renew the Wi-Fi lease and inspect the wireless infrastructure |
| Both wired and Wi-Fi | Shared router/DHCP configuration or Windows networking state is more likely | Check the DHCP service, then perform the Windows reset sequence |
Isolate a wired hardware problem
Hardware testing is warranted only when the warning or loss of connectivity is limited to Ethernet. A damaged cable or failing adapter can interrupt DHCP exchanges and make a wired connection appear inconsistent.
- Shut down or disconnect the Ethernet link, then reconnect it firmly at both ends.
- Try a known-good Ethernet cable that works with another device.
- Move the cable to another known-working switch or router port.
- If available, test with a known-good USB-to-Ethernet adapter. Install its manufacturer-provided driver through the normal Windows update or device-support process.
- Run
ipconfig /allafter each change and note whether the conflict follows the cable, port, adapter, or computer.
If the same address conflict follows the network rather than one physical component, return to DHCP scope, reservations, and ARP/DAD checks. Replacing a cable cannot correct two devices being assigned the same IPv4 address.
What not to do
- Do not disable duplicate-address detection just to suppress the notification.
- Do not assign a random static address inside the router’s DHCP pool.
- Do not run
ipconfig /releaseand assume the problem is solved when the warning repeatedly returns. - Do not enable a spare router’s DHCP service on a network that already has an active DHCP server.
- Do not treat a conflict warning as proof of an attack; verify the lease, reservation, and MAC-address evidence first.
When the problem is resolved
A successful fix has three signs: the affected adapter receives one valid IPv4 address, the gateway and DHCP server are the intended devices, and the warning does not return after reconnecting or restarting. Save the corrected reservation or static-address record, especially on a managed network, so future equipment changes do not recreate the overlap.
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