Expecting 300 mbps upload speed but only getting 20 mbps upload

I just upgraded my plan as I was tired of having 20 mbps uploads, which I had assumed was due to having a plan with 35 mbps upload. So I upgraded to the 2 gigabit plan (which shows 2k mb down, 300 mb up).

Now my download is killing it, speedtest.net shows it at a 2300+ mbps rating, but my upload is still stuck at/under 20.

My modem is the Arris S33v2, which has docsis 3.1 -- it's on the list of approved modems for the speed, and clearly it is capable, at least of the download task.

I've tried to bypass the router to see if the router I'm using is an issue, but I still get 16-20 mbps upload. I feel like something isn't working correctly, as my modem says it's operating under docsis 3.1, it's not struggling to keep a connection or anything, but it just can't get even 1/3 of the speeds I've wanted.

Let me know if there's anything I can do to fix this issue myself.

Thanks!

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Accepted Solution

BruceW

Gold Problem Solver

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26K Messages

1 month ago

The S33 modem is compatible with 2 Gbps internet speed, but is not compatible with the new higher upload speeds. Only a few retail devices are. See the "Next Gen" list at the top of the "All Compatible Devices" link near the bottom of https://www.xfinity.com/support/devices (at the moment it points to https://assets.xfinity.com/assets/dotcom/projects/cix-4997_compatible-devices/2024.09.18%20Full%20List%20of%20Compatible%20Devices.pdf, but this changes from time to time).

Also see:

https://www.reddit.com/r/Comcast_Xfinity/wiki/knowledgebase/next-generation-internet/ (the device list is out of date)
https://www.xfinity.com/support/articles/upgraded-areas-leased-equipment-required-for-upload-speeds

For faster upload you need one of Comcast's newer rental gateways (XB6, XB7, XB8) or one of the few retail devices shown in the "Next Gen Speed Tier" group with an upload speed rating in the "All Compatible Devices" PDF:

Hitron Technologies CODA or CODA56
Netgear CM2500, CM3000, or CBR750
ARRIS/Surfboard G20, G34, G36, G54, or S34
Ubiquiti UCI

The Reddit link lists the approved devices (although that list is out of date) as well as other requirements for faster upload speeds.

Realize that although Comcast calls some devices "Compatible" and some "Recommended", for all but a few devices those designations only mean "compatible/recommended for use with their Internet service", and not necessarily approved for the new upload speeds.

Comcast could make all of this much simpler and clearer, but they have chosen not to do so.

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user_rqgdu5

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@BruceW

I have an XB8 through Xfinity and I have the same plan as the customer who posted their issue. I am paying for 2000mbps(only getting 1,400)/300mbps upload(only getting 30MBPS) so if what you are saying is accurate, why am I getting upload speeds 10x weaker than what I pay for.

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14 days ago

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XfinityBrianH

Official Employee

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935 Messages

1 month ago

mad626rad Can you please send us a DM. You can start by clicking the chat icon located in the top right corner of your forums' page when signed in. Once there, you can direct your messages to "Xfinity Support." Please add your full name and service address to help us locate your account. Let me know if you have any questions.

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mad626rad

Expecting 300 mbps upload speed but only getting 20 mbps upload

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