This topic

Wired IP issues using BT Smarthub 2 and Orbi RBR20 in router mode

dansapple — Sat, 09 Aug 2025 09:09:01 GMT

Hi all,

I’m having wired DHCP challenges with a bt smarthub 2 and Orbi RBR20 router setup. And help appreciated!

Setup:

BT Smart Hub 2 connected to phone line.
DMZ on Smart Hub pointing to the WAN IP of my Orbi RBR20 router.
Orbi RBR20 in router mode with its own DHCP enabled.
Orbi WAN port connected to Smart Hub, Orbi LAN port connected to an unmanaged switch feeding wired devices around the house (TV, Sky Q, etc.).

Problem:

Wi-Fi devices on the Orbi work perfectly.
Wired devices via the switch fail to get an IP address or internet connection.

Questions:

Is it expected that the BT Hub’s DHCP would still be active for wired devices even when DMZ is configured to point to the Orbi?
Would I need to fully disable DHCP on the BT Hub to avoid IP conflicts?
Could this be a limitation of my older 100mbps unmanaged switch not passing DHCP correctly?
Would it be better to have the smarthub manage DHCP and the Orbi in AP mode?

Any advice would be appreciated!

Re: Wired IP issues using BT Smarthub 2 and Orbi RBR20 in router mode

licquorice — Sat, 09 Aug 2025 09:52:45 GMT

Simple enough to just disable DHCP on the hub and see what happens.

As with most things IT, trial and error is the best course of action.

Re: Wired IP issues using BT Smarthub 2 and Orbi RBR20 in router mode

dansapple — Sat, 09 Aug 2025 10:43:01 GMT

Tried switching off DHCP on the BT Hun, but that didn’t work either.

Easiest workaround, which seems to have worked, was to simply put the ORBI router into access point mode, and have BT manage DHCP.

Re: Wired IP issues using BT Smarthub 2 and Orbi RBR20 in router mode

Crimliar — Sun, 10 Aug 2025 20:31:51 GMT

It sounds as if you originally had the Orbi using the same subnet (192.168.1.0/24) as you were using for the BT router. If that's the case, then your WiFi devices working was probably just a happy accident. If you can do everything you need to do with the Orbi devices in AP mode then run with it! If not there are plenty of examples on these boards about how to most successfully get "double-NAT" to work!