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user_xrcap3
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Wednesday, June 24th, 2026 6:13 PM

XB8 stuck on sub-split upstream -- no mid-split, upload capped at 35 Mbps

My XB8 (CGM4981COM) is ranging only on sub‑split upstream channels (10–40 MHz), with no mid‑split and no OFDMA upstream, so my upload is capped at ~35 Mbps despite a 1.2 Gig plan. Please check whether mid‑split is live on my node, and if so push the enhanced‑upload bootfile and re‑provision my upstream. If frontline can't, please open an engineering ticket.

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27 days ago

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user_xrcap3

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28 days ago

Following up — still seeing sub‑split‑only upstream, no OFDMA; can someone from Xfinity Support take a look?

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lcag123

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28 days ago

Hi im having the same problem neighbor has lower speed plan there getting over 100mb upload im stuck at around 40mb upload on Gigabit extra we both have a xb8 gateway? My signals levels are even better to then there's we both have ofdm on both download and upload signals. so must be the configuration boot file ? Reason im not getting mid or high split speed we both are wired direct to street no splitters at all.

What should i do to fix mine can you send a update ?

(edited)

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XfinityMarshante

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27 days ago

Hello @user_xrcap3, thank you for taking the time to leave a post. Sorry to hear you’re experiencing issues with your upload speeds. I can understand how frustrating that must be, especially when you’re expecting improved performance but are still seeing the older speeds. When testing the speeds, are you hardwired directly to the modem or wireless? 

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user_xrcap3

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  Thanks @XfinityMarshante. Yes — I'm testing hardwired via Ethernet directly to the gateway (Xfinity XB8 / CGM4981COM), so it's not a Wi-Fi limitation. Wired,
  upload tops out around 35-36 Mbps.                                                                                                                            
                                                                                                                                                                
  A few things I've already verified that point to the node rather than my setup:                                                                               
  - My gateway's upstream is ranging only on legacy sub-split SC-QAM channels (10-40 MHz) — no OFDMA upstream and no mid-split (42-85 MHz) channels at all.     
  - In the "Change speed" tool, every tier offered at my address (300 / 500 / 1 Gig / 1.2 Gig) lists the same ~41 Mbps typical upload — so a plan upgrade       
  wouldn't change anything.                                                                                                                                     
                                                                                                                                                                
  That looks like my node hasn't been upgraded to mid-split / DOCSIS 4.0. Could you please confirm:                                                             
  1. Is mid-split / DOCSIS 4.0 enabled, or on the near-term roadmap, for the node/CMTS serving my address?                                                      
  2. Is there any plan at my address that offers higher upload than ~35-41 Mbps?                                                                                
                                                                                                                                                                
  Happy to move to a direct message with my account details so you can look it up. Thanks!                                                                      

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27 days ago

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XfinityJustinM

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Hi @user_xrcap3, 

You've asked some good questions! The Xfinity.com/labels website is the most up-to-date website that shares the current speeds available in your area. I assume you are already using this since you mentioned the typical upload speed. The information you provided would indicate that your area is currently on our base/sub-split network infrastructure. The upload speeds for our base tiers have all been set to receive that up to 35 Mbps upload speed. There are currently no roadmaps for when nodes will be upgraded to our enhanced speeds. What other questions do you have related to this topic? 

(edited)

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27 days ago

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