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I have Cox gigablast and was getting 940Mbps speeds with my Motorola MB8600. I’ve “upgraded” to the Arris S33 and S34 and I’m getting weird results with the 2.5G port. Both modem continue to download at 940Mbps when connected to the 1G port. However, when connected to the 2.5G port, I only get between 180-300Mbps. I’ve tried multiple laptops, desktops, and switches with 2.5G ports. I’ve also used Cat6a and Cat 8 cables but the results are all consistent. I would assume I would continue to get 940Mbps when connected to the faster 2.5G port. Also worth noting is that I do not get a link/connection light on any of the modems’ ethernet ports, but the respective activity light flashes green when connected to either port. And of course, I’ve rebooted the modem with and without the ethernet connected to either port. I returned the S33 thinking it was defective and the purchased the S34 which demonstrates the same issue.

Is this a firmware issue or does the carrier need to enable the 2.5G port?

It sounds as though your ISP may have registered the 1G port MAC address as opposed to the 2.5G port. This is just a guess given your description.

I doubt that it is a firmware issue. Hope this helps.

I have Cox as well & just upgraded to their 2 gig service. I agree w/ the other reply. Try calling Cox tech. support (a pain, I know), discuss it w/ them & see what they suggest. But regardless of what they say, personally I’d just insist on re-setting your modem. I would take it back to factory settings (utilize paper clip or such to hit the reset - you probably know how already) & have Cox freshly rebuild the connection plugging into the 2.5 port. Worked for me. Best of luck! 🍀

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