IP address conflict 0X00000263 — two PCs fighting over the same IP

When this error hits

You're working away and suddenly your network connection drops. A balloon pops up from the system tray saying 'There is an IP address conflict with another system on the network.' If you run ipconfig in Command Prompt, you see an IP like 169.254.x.x — that's your PC failing to get a proper address. Or worse, you're using a static IP that another device on the same subnet already claimed. This usually happens right after you plug in a new laptop, reboot your router, or wake your PC from sleep on a busy office network.

Why it happens

Every device on your local network needs a unique IP address. Your router's DHCP server hands them out. But if two devices end up with the same IP — because of a stale DHCP lease, a static IP that overlaps with the DHCP pool, or two devices both thinking they own that address — Windows throws error 0X00000263. The real fix is to force your PC to let go of the old address and grab a fresh one that nobody else is using.

The fix — numbered steps

1. Open Command Prompt as admin. Click Start, type cmd, right-click 'Command Prompt' and pick 'Run as administrator.' Click Yes when UAC asks.
2. Release your current IP. Type ipconfig /release and press Enter. You'll see all your network adapters lose their IP — they'll show 0.0.0.0. That's normal.
3. Renew with a fresh IP. Now type ipconfig /renew and press Enter. Wait up to 30 seconds. After it finishes, run ipconfig again. You should see your adapter has a valid IP starting with 192.168.x.x, 10.x.x.x, or 172.16.x.x. If you still see 169.254.x.x, skip to the 'Still failing' section below.
4. Clear the ARP cache. Type arp -d * and press Enter. This wipes the local table that maps IPs to MAC addresses — prevents your PC from trying to talk to the old, conflicting device.
5. Reboot your network adapter. Open Network Connections — press Win+R, type ncpa.cpl, hit Enter. Right-click your active adapter (usually 'Ethernet' or 'Wi-Fi'), pick 'Disable.' Wait 5 seconds, right-click again and pick 'Enable.'
6. Check for static IP conflicts (if you use a static IP). Right-click your adapter in ncpa.cpl, pick 'Properties,' double-click 'Internet Protocol Version 4 (TCP/IPv4).' If 'Use the following IP address' is selected, make sure the IP isn't already in use. Easiest test: temporarily switch to 'Obtain an IP address automatically,' apply, then run ipconfig /renew. If that works, your static IP was the problem. Pick a different static IP outside your router's DHCP range.

Still failing? Check these

• Router DHCP settings. Log into your router (usually 192.168.1.1 or 192.168.0.1). Look for 'DHCP server' or 'LAN settings.' Make sure the pool of addresses it hands out (the start and end IP) doesn't include any static IPs you set manually. If your router leases addresses from 192.168.1.100 to 192.168.1.200, don't set a static IP like 192.168.1.150.
• Multiple devices with the same MAC. Rare, but some cheap network cards clone MAC addresses. Run getmac in Command Prompt to see your PC's MAC. Compare it to other devices on the network — if they match, you need to change the MAC on one of them. On your PC, go to adapter properties, click 'Configure,' go to the 'Advanced' tab, find 'Network Address' or 'Locally Administered Address,' and enter a different 12-character hex value (like 020000000001).
• Reset the whole network stack. In an elevated Command Prompt, run these three commands one at a time: netsh int ip reset, netsh winsock reset, and ipconfig /flushdns. Then restart your PC.

If none of that works, the conflict is probably on the router itself — power-cycle it (unplug for 30 seconds, plug back in). That clears its ARP table and forces every device to re-negotiate IPs from scratch. Nine times out of ten, that's the real fix.