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Arris Surfboard 6121 (Customer owned) issues

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Message 1 of 6
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I have an Arris Surfboard 6121 that should be capable of 172 Mbps down, but is only getting 30mbps. The speedtests all put it right up against 30, clearly maintaining some sort of throttling to keep it from going beyond. I was receiving 75 mbps down in Knoxville, TN with no issues until I recently moved to a different major city in Tennessee. I have called Xfinity 4 times and spent 3 hours on the phone in the last week to try to resolve issues I'm having. I paid for 300mbps down due to a good promotional offer with a 3 yr commitment, which I'm now deciding was probably a huge mistake given the quality of customer support.

 

I was initially getting 25mbps down capped. After my first call with Xfinity I was informed there was an issue with End of Life regarding the 6121, but we were able to increase the speed to 30mbps down. After questioning that, she said nevermind that's only for Xfinity leased modems and that she would escalate my issue...

 

Fast forward to today, I called back only to be told my issue was escalated but rejected since it is a customer owned modem. In fact, I was told, no troubleshooting beyond the basics can be done on Non-Xfinity owned equipment. I have received no explanation as to why it was possible to get 75 mbps down 4 months ago, but only 30 now. I've been reassured though, that there is nothing to be done and sorry for my troubles. I am going to cancel and go with AT&T Fiber if this can't be resolved in the next few days, but really don't want to spend more of my free time dealing with Xfinity not actually cancelling my account and not refunding the amounts I have already paid as well as getting new service set up with ATT. Any help is appreciated.

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Posted by
Connection Expert

Message 6 of 6
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Solution

graypickney wrote:

If im getting the speed config file for 25/5, why are my speeds capped at 30mbps?


There is 20% speed over-provisioning involved. 25 nets 30. 200 nets 240. 5 nets 6, 10 nets 12. etc. etc.




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5 REPLIES
Posted by
Connection Expert

Message 2 of 6
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The modem is not compatible with a 300 Mbps speedtier so it defaults to using a "Performance Tier" (25/5) configuration file from their system.

 

Go here and input your info to find a compatible modem that will acccept a faster config file;

 

https://mydeviceinfo.xfinity.com/customerinfo




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Message 3 of 6
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If im getting the speed config file for 25/5, why are my speeds capped at 30mbps?

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Message 4 of 6
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Follow up: 

 

Do they not have the ability to give me the config file for the 150mbps service until such a time that I can upgrade my modem?

Posted by
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Message 5 of 6
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graypickney wrote: ... Do they not have the ability to give me the config file for the 150mbps ...

They could, but they don't. They rate the top speed of the 6121 at 101 Mbps (see https://mydeviceinfo.xfinity.com/device/arris-sb6121-365), so it might not even work with their 105 Mbps service.

Posted by
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Message 6 of 6
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Solution

graypickney wrote:

If im getting the speed config file for 25/5, why are my speeds capped at 30mbps?


There is 20% speed over-provisioning involved. 25 nets 30. 200 nets 240. 5 nets 6, 10 nets 12. etc. etc.




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