Networking: Clients receive the wrong default gateway or DNS server — a rogue DHCP server (often a home router) answers first
A second DHCP server on the network is giving clients bad settings, so some machines have no internet or odd DNS.
rogue DHCP serverwrong default gateway from DHCPDHCP server handing out wrong DNSsecond DHCP server on the networkunauthorized DHCP server Meaning
Compare ipconfig /all and look at "DHCP Server" on a broken client. Find the rogue device (a home router plugged into the LAN via a LAN port, a VM bridge, an ICS share) and disable its DHCP, then enable DHCP snooping on switches so only trusted ports can answer.
Common causes
- Consumer router plugged into the office LAN
- VM or hotspot bridging DHCP onto the LAN
- Internet Connection Sharing enabled
- Misconfigured second DHCP server
- No DHCP snooping on switches
⚡ Quick fix
- Check the DHCP server address:
ipconfig /all - Unplug/disable the rogue DHCP
- Enable DHCP snooping with trusted uplink ports only
Detailed fix by platform
Windows
- powershell
ipconfig /all | findstr /i "DHCP Server Default Gateway DNS" nmap --script broadcast-dhcp-discover
How to diagnose
- DHCP server — Expected address?
- Second offer — Present?
- Snooping — Enabled?
🔧 Still not fixed?
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Other ways to find it
Where this error sits
Origin: Network. Errors that are often confused with or caused by this one (click to open):
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Last updated 5 Nov 2026