Another Case of RBR50 with Spectrum MODEM

Orbi RBR50 SN 5VG1935K08580

Firmware v2.7.5.6

Router works fine with Brightspeed vDLS2 MODEM and with Starlink V3 MODEM.

Connected today to Spectrum 1G Cable Internet service. Tried to plug directly into Spectrum Cable MODEM

Spectrum Model EU2251 DOCSIS 3.1 eMTA

I noticed that the only output port of the Cable MODEM is marked 2.5G.

Other MODEMs have 1G ethernet outputs.

I connected the Spectrum Wifi Router (with built in ethernet switch) to the Spectrum DOCSIS MODEM and then connected the Orbi RBR50 to one of the 1G ethernet ports on the back of the Spectrum Wifi Router. It works fine that way.

I would think that a 2.5G ethernet switch should be backward compatible to 1G ethernet. But in case I'm wrong: can the RBR50 connect to a 2.5G ethernet port?

Thanks for your help.

EdwardMac
Feb 28, 2025
CrimpOn Thank you very much for all your help. I followed the procedure you detailed three times. (twice yesterday and once again today, this time waiting 20 minutes for router to connect to the internet, which it didn't).

But your instructions did inspire me to go to the Orbi app and attempt a "New Setup". The secret sauce with making this work, apparently, is to power both MODEM and router off, connect the ethernet cable between them, and then power both on (connecting power cables) at the same time. When doing this, the router was able to connect to the internet. The "New Setup" procedure never got to the "Connect to local router WIFI" step: the router had already connected to the internet and was servicing devices on the network.

Thank you again. I appreciate your patient help.

4 Replies

CrimpOn
Guru - Experienced User
Feb 27, 2025
EdwardMac wrote:

I would think that a 2.5G ethernet switch should be backward compatible to 1G ethernet. But in case I'm wrong: can the RBR50 connect to a 2.5G ethernet port?

Yes, 2.5, 5, and 10G Ethernet ports are generally backward compatible with 1GB.

Should connect just fine.
- EdwardMac
  Tutor
  Feb 28, 2025
  Thank you.
  May I ask you your opinion on the failure? Since the RBR50 doesn’t work with the Spectrum MODEM 2.5G port, is it safe to say that the problem is the Spectrum MODEM?
  - CrimpOn
    Guru - Experienced User
    Feb 28, 2025
    Spectrum documentation clearly states this modem supports multiple Ethernet speeds:
    
    The typical procedure is to:
    
    power off the modem
    
    connect the customer router WAN port (often Yellow) to the modem Ethernet port
    
    power up the modem and wait until the lights stabilize
    
    power up the customer router

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Another Case of RBR50 with Spectrum MODEM