What this page covers
Compare DHCP-server and gateway fields from two clients, then isolate the unauthorised router or extender.
Step-by-step workflow
- Capture configuration fields from two affected clients privately.
- Identify every router, access point, extender and hotspot attached by Ethernet.
- Disconnect one suspected device at a time from the LAN.
- Keep the intended DHCP authority and retest new leases.
Decision table
| Check | What it tells you | Safe next action |
|---|---|---|
| Different gateways | Clients are receiving different offers | Find the second DHCP source |
| Different DNS servers | DHCP scopes or policy differ | Compare router LAN settings |
| Only guest devices fail | Intentional isolation may be involved | Check the guest network design |
Limits and verification
Do not disable a provider-managed gateway without understanding bridge, voice, TV or support dependencies.
Official sources
- IETF RFC 2131 — Dynamic Host Configuration Protocol (DHCP message and lease concepts)
- CISA — Securing Home Network Devices (home-network safety guidance)
Related Router Portal guides
Find the current gateway · Router security guide
Keep in mind: Firmware, operating-system menus, ISP policies and regional radio rules can change. Confirm the current official source and exact device before applying a setting.
Our networking steps are lab-tested against standard RFC 1918 private networking protocols across Windows 11 (24H2), macOS Sequoia (15.1), iOS 18, and Android 15. We verify physical device labels and firmware release documentation before publishing gateway instructions. Router Portal is strictly read-only and never requests, intercepts, or logs router passwords.