Paying for 600Mbps, Getting less than half. CM1000 modem + Nighthawk AC1900 router

[banjo_viking]

This issue has already consumer hours of my time and has forced me to get an advanced education in routers and modems that I never wanted. When I stand next to my router on 5G bands, I should be able to get something close to the 600Mbps I am paying for, but I can only get a max of 150-280Mbps (using multiple speed test sites). Not bad, but nowhere near where it should be. When the Xfinity techs plug in their own Gateway modem/router, low and behold they get 450-580. Something is up.

I've done ALL the standard procedures (power cycling, ordering, replacing Cat5 with Cat6, checking power adapters, etc.)

My house is a brand new construction (2020), so I doubt it's a cable. We don't have TV, so there is no cable splitting. Techs confirmed I'm getting "beautiful" signals to the house, and they have no issues with their modem/router, so I have to think it's my modem.

My modem is a recommended model per Xfinity. CM1000 Docsis 3.1. It's speaking fine with the router, which is an R7000 Nighthawk (AC1900). Again, more than capable of handling the speeds. All firmeware is up to date, per the Netgear techs.

Some irregularities I've noticed:

• The wifi speed is MUCH faster than the Ethernet speed, which sits around 100 or less. I've only tested on one laptop, so there's a chance the modem ethernet port or the laptop ethernet port are capped at 100Mbps, but that seems less likely to me for a CM1000 and a 2017 laptop. The Ethernet speeds are the same whether I'm plugged into the router or directly into the modem.

• I'm only getting 4 upstream channel bonds. Not sure if I should be getting more.

• My log keeps throwing a dynamic range window violation code saying my power is too high, which you can confirm below, but it doesn't appear to be a major interruption to service. I've yet to notice dropped internet, only slower internet than I should be getting.

At this point, I'm thinking new modem, new router, or both. But I just bought this setup so I would hate to giveup on it too easily. Any advice would be stupendous. Thanks

<tabindex=-1>Startup Procedure</tabindex=-1>

Procedure Status Comment Acquire Downstream Channel 573000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Security Enable BPI+ IP Provisioning Mode Honor MDD IPv6 only

<tabindex=-1>Downstream Bonded Channels</tabindex=-1>

Channel Lock Status Modulation Channel ID Frequency Power SNR / MER Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked QAM256 25 573000000 Hz 8.2 dBmV 40.5 dB 52706848 11 23 2 Locked QAM256 13 501000000 Hz 9.0 dBmV 41.0 dB 60886218 25 8 3 Locked QAM256 14 507000000 Hz 9.4 dBmV 40.9 dB 60891019 15 19 4 Locked QAM256 15 513000000 Hz 8.9 dBmV 40.9 dB 60894264 25 0 5 Locked QAM256 16 519000000 Hz 8.8 dBmV 40.8 dB 60897561 28 4 6 Locked QAM256 17 525000000 Hz 9.0 dBmV 40.7 dB 60901251 30 0 7 Locked QAM256 18 531000000 Hz 8.8 dBmV 40.8 dB 60906027 10 24 8 Locked QAM256 19 537000000 Hz 8.8 dBmV 40.8 dB 60908896 30 0 9 Locked QAM256 20 543000000 Hz 8.7 dBmV 40.7 dB 60919582 27 6 10 Locked QAM256 21 549000000 Hz 8.2 dBmV 40.5 dB 60926039 10 24 11 Locked QAM256 22 555000000 Hz 8.5 dBmV 40.6 dB 60929568 17 16 12 Locked QAM256 23 561000000 Hz 8.6 dBmV 40.6 dB 60932399 20 12 13 Locked QAM256 24 567000000 Hz 7.9 dBmV 40.4 dB 60937218 27 0 14 Locked QAM256 1 411000000 Hz 8.7 dBmV 40.8 dB 50828218 32 0 15 Locked QAM256 26 579000000 Hz 8.5 dBmV 40.5 dB 60944562 15 19 16 Locked QAM256 27 585000000 Hz 7.8 dBmV 40.3 dB 60948429 11 23 17 Locked QAM256 28 591000000 Hz 8.0 dBmV 40.5 dB 60970782 11 24 18 Locked QAM256 29 597000000 Hz 9.1 dBmV 40.6 dB 60976095 8 25 19 Locked QAM256 30 603000000 Hz 8.2 dBmV 40.4 dB 60979616 5 29 20 Locked QAM256 31 609000000 Hz 7.7 dBmV 40.2 dB 60983303 8 26 21 Locked QAM256 32 615000000 Hz 9.0 dBmV 40.3 dB 60986448 10 24 22 Locked QAM256 2 417000000 Hz 8.4 dBmV 40.9 dB 50948097 33 0 23 Locked QAM256 3 435000000 Hz 8.4 dBmV 40.9 dB 50962136 18 15 24 Locked QAM256 4 441000000 Hz 8.3 dBmV 40.9 dB 50973413 26 4 25 Locked QAM256 5 453000000 Hz 8.8 dBmV 41.2 dB 50983532 7 26 26 Locked QAM256 6 459000000 Hz 8.5 dBmV 40.9 dB 50996652 14 19 27 Locked QAM256 7 465000000 Hz 9.2 dBmV 41.0 dB 51011301 26 5 28 Locked QAM256 8 471000000 Hz 9.2 dBmV 41.0 dB 51024527 26 7 29 Locked QAM256 9 477000000 Hz 8.8 dBmV 41.1 dB 51033669 27 0 30 Locked QAM256 10 483000000 Hz 9.2 dBmV 41.1 dB 51047600 31 2 31 Locked QAM256 11 489000000 Hz 9.6 dBmV 41.1 dB 51053459 9 25 32 Locked QAM256 12 495000000 Hz 8.9 dBmV 41.0 dB 51058490 27 4

<tabindex=-1>Upstream Bonded Channels</tabindex=-1>

Channel Lock Status Modulation Channel ID Frequency Power 1 Locked ATDMA 5 36100000 Hz 41.0 dBmV 2 Locked ATDMA 6 29600000 Hz 41.3 dBmV 3 Locked ATDMA 7 23000000 Hz 40.5 dBmV 4 Locked ATDMA 8 16500000 Hz 40.5 dBmV 5 Not Locked Unknown 0 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Hz 0.0 dBmV

<tabindex=-1>Downstream OFDM Channels</tabindex=-1>

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power SNR / MER Active Subcarrier Number Range Unerrored Codewords Correctable Codewords Uncorrectable Codewords 1 Locked 0 159 722000000 Hz 9.2 dBmV 39.5 dB 1246 ~ 2849 3214687535 23993 0 2 Not Locked 0 0 0 Hz 7.6 dBmV 0.0 dB 0 ~ 4095 0 0 0

<tabindex=-1>Upstream OFDMA Channels</tabindex=-1>

Channel Lock Status Modulation / Profile ID Channel ID Frequency Power 1 Not Locked Unknown 0 0 Hz 0 dBmV 2 Not Locked Unknown 0 0 Hz 0 dBmV

[Shankarhokie]

Have you tried connecting to the modem directly and conducted a speedtest? 

Did you check speeds here?  https://speedtest.xfinity.com/

Also, look at the max possible wifi speeds for various devices https://speedtest.xfinity.com/devicespeeds

[banjo_viking]

Thanks for the reply.

Yes, I've run several speedtests at different times of the day. When I'm plugged directly into the modem, I achieve speeds of 100Mbps or less. Same thing when I'm plugged into the router. When I use Wifi, I can get 150-280Mbps. 

[BruceW]

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@banjo_viking wrote: ... My log keeps throwing a dynamic range window violation code ...

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Please post the complete error log.

You may be able to check the laptop's Ethernet adapter speed by checking its device characteristics. If it's running Windows, you can do that in Device Manager / Network adapters.

[banjo_viking]

Thanks.

I think I was able to solve my problem, but I don’t know if I solved it so much as I bypassed it.

I had an extra modem and router that were the same models as the one’s I’ve been struggling with, so I decided to swap them out one by one to see if that made a difference. Changing modems made no difference, but switching out the router did make a small difference—nothing drastic though.

I went to the store and bought a very inexpensive wifi-6 router, and suddenly my WiFi speeds are at full capacity! I’m clocking in now at 580 mbps when I stand next to the router. The hard line speeds are still coming in at 100 and lower, thought, and they did not change across the two modems and three routers. I’m starting to think it has something to do with my computer and not my boxes. I’ll have to try connecting in with a different laptop soon to see if that makes a difference.

Thanks everyone