Visitor
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2 Messages
Upload speed capped at 40 Mbps - Boot file (d11_m_b12_subnxmid_c01.cm) failing validation on Motorola B12
I'm writing about a persistent upload speed issue on my account that I believe is tied to a failed boot file delivery to my cable modem, not a signal/line issue.
Background:
- Previous modem: Xfinity CGM4331COM (xFi Advanced Gateway/XB7). On my 300 Mbps plan, I consistently got 180 Mbps upload. After upgrading to the 500 Mbps plan (same gateway, no hardware change), upload dropped to 120 Mbps.
- Current modem: Motorola B12 (model B12-30-10), still on the 500 Mbps plan. Upload is now capped at 40 Mbps, down from 120 Mbps on the same line with the previous gateway.
- Since my previous gateway held 180 Mbps consistently on this same line, I don't believe this is a physical line/plant degradation issue.
What I found in the modem's event log:
The modem shows repeated attempts by your network to change the upstream diplexer mode toward a wider mid-split (5-85MHz), which keep failing and reverting to the default low-split (5-42MHz). Specifically:
SW Download INIT - Via Config file d11_m_b12_subnxmid_c01.cmError: Code File Manufacturer CVC Validation FailureError: SW upgrade Failed after download - SW File corruptionThis suggests the boot/config file needed to enable mid-split upload on this modem is failing validation or downloading corrupted, rather than my account lacking eligibility for higher upload speeds.
What I'm asking:
- Can you confirm the correct boot file that should be assigned to a Motorola B12 on my plan/mid-split tier?
- Can you apply the account-level code some reps have used to force the correct boot file to be resent to the modem? (I understand this doesn't affect plan/pricing, just forces a re-push.)
- If this can't be resolved remotely, can this be escalated to Tier 2/technical support rather than standard troubleshooting steps (power cycling, etc.), since I've already ruled those out?
Modem details:
- Model: Motorola B12 (B12-30-10)
- CM-MAC: [Edited: "Personal Information"]
Happy to provide additional log excerpts or a screenshot of the modem's status page if helpful.
XfinityCliff
Official Employee
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594 Messages
18 hours ago
Hi @user_x6pnbd, thank you for providing those details and the troubleshooting you've already completed here on our Xfinity Community forums.
We can certainly understand why you'd be concerned, especially given the differences in upload speeds you've experienced between your previous gateway and the Motorola B12.
The Motorola B12 is not currently listed as a device that supports Xfinity's Next Generation Speed Tier upload enhancements. As a result, its upload performance may differ from Xfinity gateways or customer-owned devices that are certified for those higher upload speeds.
You can view the latest list of compatible and Next Generation Speed Tier-supported modems here: Customer-Owned Modems. We would be happy to assist you with switching back to an Xfinity Gateway, or you could replace yours with one that is compatible with Next Generation speeds from Xfinity.
Please let us know if you have any additional questions.
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