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Saturday, May 9th, 2026

SB8200 not showing DOCSIS 3.1 OFDM

Anyone have any idea why a used SB8200 would connect to OFDM on downstream(blue downstream light) but a brand new SB8200v3 would not? I tried the old modem first, before opening the new one I bought Incase used one didn't work. New account, self install. Used one got online(self reg 172 IP) with the blue downstream light but wasn't giving me the diagnostic UI. I thought it was an issue with modem so called and had new modem added to account. At first the Rep only asked for the model number and said he didn't need S/N or HFC MAC. When that obviously didn't work he tried to transfer me to Technical(he was sales) but hung up on me. So I call back and someone in Tier 1 fixes the problem and I am online direct to laptop. Hang up and go to connect router but WAN won't pull DHCP no matter how many times I power cycle. Modem ended up needing factory reset to give router public IP.

So long story short I am online but not sure why my modem lights aren't correct. If I could see that my signal levels were within spec I would just call it a day, but Cox blocks the 192.168.100.1 diagnostics now. Tier 1 cant see levels anymore and says cant get me to Tier 2 since I have a retail modem. I fear any issue causing OFDM not to connect may cause intermident issues. I basically just need to know if I should wait if a firmware update will fix the issue overnight or if I need to bypass the single splitter at the Dmarc. Please advise. Thank you.

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479 Messages

5 days ago

Hello BiPolaris,

I would recommend waiting another day to allow the firmware to update.  Feel free to send us an email with your account details to cox.help@cox.com if we need to add the correct modem to the account.  
-Latitia

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2K Messages

4 days ago

Whenever you change the device connected to the modem, you have to reboot the modem. 

Cox DHCP see's that an IP address was provided to a specific MAC ID, and when you change the device connected to the modem, you change the MAC ID the modem see's and Cox says, "I already gave you an IP, no second IP will be provided". That's why the modem has to be restarted. 

That being said, if you request escalation to CAG, (there is no longer a Tier 2, I was part of Tier  2 when we were all made part of the CAG, Customer Advocacy Group), They should transfer you, retail modem or not. 

Also, a brand new modem may not have the latest firmware on it. Leaving it connected for a few days, should get any new/updated firmware installed by Cox's Docsys Engineering.

Lastly, Cox does NOT block 192.168.100.1. That's a direct shot between your device and your Modem. Cox cannot block that.  See picture, I accessed my netgear modem

User uploaded image

(edited)

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