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DOCSIS 3.1 connectivity problem with ARRIS SB8200
I replaced my DOCSIS 3.0 modem DOCSIS 3.1 one (ARRIS SB8200) after upgrading my Xfinity internet plan (500Mbps to 1100). I was able to connect the new modem using the Xfinity app, but I'm only getting 600Mbps. The LEDs indicate the connection is operating at DOCSIS 3.0, not 3.1 - RECEIVE/downstream is blue (3.1), but SEND/upstream channel is green (3.0). I chatted with Xfinity agents for quite a while and they supposedly made some changes but it made no difference in speed. Any suggestions on where I can go from here?
Accepted Solution
EG
Expert
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111.3K Messages
24 days ago
@jplloyd
We've seen posts here indicating that what happens is that if you use an incompatible modem for a faster speed tier, the modem will default down to using an even slower speed configuration file. This is likely why you're only getting 600 down. I don't really understand why this is done..... A compatible device must be used.
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NoNoBadPuppy
Problem Solver
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684 Messages
25 days ago
The Arris SB8200 is rated for 1GB speed only, but when you factor in the overhead required it actually drops it down to close to 900. I used one for years, but switched it out for one that supports speeds above 1GB. You will not get either 1GB or faster with that modem. It was a great modem in it's day, but is a little dated today.
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plumld
Contributor
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267 Messages
25 days ago
The top speed of the SB8200 (I had one) is 940 and 40 down, without the Mid-Split, using an Ethernet connection. I have a 1300/35 plan and changed to a Netgear CM3000, changing my infrastructure to a 2.5Gbps network. I now get 1500/40, still waiting for the Mid-Split upgrade.
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BruceW
Gold Problem Solver
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26.5K Messages
24 days ago
Although I haven't been able to find a crystal-clear statement on this, I suspect that upstream-green means you only have QAM upstream channels, which is standard for modems that aren't running the higher upstream speeds introduced in 2023.
Upstream-blue would mean the modem is also using OFDMA upstream channels, which isn't happening because Comcast/Xfinity doesn't consider the SB8200 compatible with its NextGen/Enhanced Speed service which uses those channels.
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BruceW
Gold Problem Solver
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26.5K Messages
23 days ago
Cite?
The specs Arris posted at https://arris.file.force.com/sfc/dist/version/download/?oid=00D30000000kUAL&ids=068Qi00000813P5IAI&d=%2Fa%2FQi000000toqb%2F_NtbhWQP5jcDyNJSRE2g_OyUbugFb6DbUHZ4myuYnbg& states:
Although possible, it would be odd for Arris to claim those specs if it did not provide the firmware to enable them.
OTOH that same page under "Interface Speeds" claims "DOCSIS 3.1 Downstream OFDM 10,000 Mbps", so maybe we shouldn't trust those claims? Even if the device can "listen" at 10 Gps it certainly can't pass data at 10 Gps.
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XfinityArmand
Official Employee
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2.2K Messages
23 days ago
Thank you so much for taking the time to reach out to Xfinity Support @jplloyd! We're so glad to hear from you and want to help in any way that we can to ensure you are having the best experience with your service. No worries! You have reached out to the best team to assist in addressing your service concern. So that we can get started, please feel free to shoot us a private message with your details, and we will get the ball rolling for you.
To send a "direct message" / "private message" message to Xfinity Support:
• Click "Sign In" if necessary
• Click the "Direct Message" icon or https://forums.xfinity.com/direct-messaging
• Click the "New message" (pencil and paper) icon
• The "To:" line prompts you to "Type the name of a person". Instead, type "Xfinity Support" there
• As you are typing a drop-down list appears. Select "Xfinity Support" from that list
• An "Xfinity Support" graphic replaces the "To:" line
• Type your message in the text area near the bottom of the window
• Press Enter to send it
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BruceW
Gold Problem Solver
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26.5K Messages
23 days ago
I don't know why Arris says "or". It really should be "and". See https://forums.xfinity.com/conversations/your-home-network/674a3cb82efed25d1c16c7bd for an typical example. For devices operating in full OFDM mode we usually see 31 or 32 active downstream QAM channels plus 1 or 2 OFDM channels, and 3 to 6 upstream QAM channels plus 1 active OFDMA channel.
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EG
Expert
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111.3K Messages
22 days ago
@plumld
Not necessarily. While it is ideal to use OFDMA in the higher frequencies offered by mid-split and high-split configurations, it can also be used in legacy low-split systems. However, its full potential and maximum benefits are realized when used with mid-split or high-split networks, which provide more upstream spectrum. My local system had an upstream OFDMA channel before the implementation of mid-split.
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