Is the Orbi RBR50 not compatible with Xfinity/Comcast with Motorola MB7621 modem?

[ChuckieCheese]

I just got Xfinity/Comcast Internet and have my own modem - Motorola MB7621. The service was activated by calling Xfinity and providing the Motorola modem MAC address and serial number. The service is activated as follow:

- Modem is shown in my Xfinity web account

- The modem received IPv6 IP address

I then connect the RBR50 (yellow port for Internet) to the modem (there's only 1 Ethernet port). However, the Orbi could not get an IP address and it just show 0.0.0.0. Same goes with the DNS. The Orbi just say "No Internet".

Xfinity tech support couldn't help because they have no knowledge of the Orbi device. 

Is there anything special I need to do to get the Orbi working with Xfinity using Motorola MB7621? Or is it not compatible?

[CrimpOn]

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@ChuckieCheese wrote:

- Modem is shown in my Xfinity web account

- The modem received IPv6 IP address

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This is the first I have heard of an Internet Service Provider (ISP) assigning only IPv6 IP addresses*.  On Spectrum, I get a IPv4 IP address.

Orbi has a setting for IPv6 and I have mine set to "Disabled".  What is your Orbi set to?

On the Advanced Tab->Advanced Settings->IPv6.

*Not to say this is uncommon.  I lead a sheltered life.

[ChuckieCheese]

@CrimpOn yeah, it's weird Xfinity assigning IPv6. In the Motorola modem Admin page, the IPv4 section is blank and I thought the modem is not working, until I noticed the IPv6.

But the problem is solved (for now). I shutdown the modem and Orbi, went do some stuff and turned back the modem, wait till it is synced, then connect the Orbi. Voila, now it works! Seems I have to shutdown the modem for 10 minutes.

[michaelkenward]

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@ChuckieCheese wrote:

I shutdown the modem and Orbi, went do some stuff and turned back the modem, wait till it is synced, then connect the Orbi. Voila, now it works! Seems I have to shutdown the modem for 10 minutes.

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The timing of the process is important. I doubt if it is the 10 minutes that matters, but it does no harm to leave a healthy time out.

The order is more important. The sequence you described is spot on. A lot of people don't wait for the modem to do its thing before they turn on the router.