DT_UM's profile

Regular Visitor

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4 Messages

Wednesday, September 11th, 2024 7:20 PM

Downstream slow MB7621 modem

Hi,

Over the last week or so I've been having trouble streaming video. Today I ran a speed test hardwired to my MB7621 to confirm speed is much less than my speed tier.  Approximately 250Mbps vs. the 1Gbps tier I'm subscribed to.  I've included the log info below.  Does anyone see any issues I can use to further my troubleshooting efforts (I've already rebooted several times). Thanks.

  Cable Specification Version DOCSIS 3.0
   Hardware Version V1.0
   Software Version 7621-5.7.1.10
   Cable Modem MAC Address
   Cable Modem Serial Number
   CM Certificate Installed
    5.7.1mp4
Startup Step Status Comment
   Acquire Downstream Channel 531000000 Hz Locked
   Upstream Connection OK Operational
   Boot State OK Operational
   Configuration File OK
   Security Enabled BPI+
System Up Time 0 days 05h:35m:47s
   Network Access Allowed

 Channel Lock Status Modulation Channel ID Freq. (MHz) Pwr (dBmV) SNR (dB) Corrected Uncorrected
1 Locked QAM256 9 531.0 -1.8 39.0 0 0
2 Locked QAM256 42 405.0 -2.6 38.9 0 0
3 Locked QAM256 43 411.0 -2.7 38.8 0 0
4 Locked QAM256 44 417.0 -2.7 38.9 0 0
5 Locked QAM256 45 423.0 -2.6 38.9 0 0
6 Locked QAM256 38 435.0 -2.2 39.0 0 0
7 Locked QAM256 39 441.0 -2.0 39.0 0 0
8 Locked QAM256 40 447.0 -1.9 38.9 0 0
9 Locked QAM256 41 453.0 -2.0 38.9 0 0
10 Locked QAM256 32 459.0 -2.1 38.9 0 0
11 Locked QAM256 34 465.0 -2.0 38.9 0 0
12 Locked QAM256 35 471.0 -1.9 38.5 0 0
13 Locked QAM256 36 477.0 -2.0 38.9 0 0
14 Locked QAM256 1 483.0 -2.0 38.9 0 0
15 Locked QAM256 2 489.0 -1.8 38.9 0 0
16 Locked QAM256 3 495.0 -1.9 38.9 0 0
17 Locked QAM256 4 501.0 -2.6 39.4 0 0
18 Locked QAM256 5 507.0 -2.5 39.4 0 0
19 Locked QAM256 6 513.0 -2.3 39.5 0 0
20 Locked QAM256 7 519.0 -2.4 39.3 0 0
21 Locked QAM256 8 525.0 -2.5 39.4 0 0
22 Locked QAM256 10 537.0 -2.1 37.6 0 0
23 Locked QAM256 11 543.0 -2.6 39.3 0 0
24 Locked QAM256 12 549.0 -2.9 39.2 0 0
Total             0 0

  Channel Lock Status Channel Type Channel ID Symb. Rate (Ksym/sec) Freq. (MHz) Pwr (dBmV)
1 Locked ATDMA 2 5120 29.2 48.5
2 Locked ATDMA 1 5120 35.6 49.0
3 Locked ATDMA 3 5120 22.8 47.3
4 Locked ATDMA 4 5120 16.4 46.3
5 Locked ATDMA 5 2560 40.4 48.8
6 Not Locked Unknown 0 0 0 0.0
7 Not Locked Unknown 0 0 0 0.0
8 Not Locked Unknown 0 0 0 0.0

Official Employee

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1.5K Messages

2 months ago

Hello, @DT_UM. Thanks for reaching our team on Forums regarding your speed concerns. I appreciate you attempting to reboot your device in hopes of getting your speeds to where it should be. Can you please make sure that the coax cable is finger tight on both the modem and wall plate, also can you confirm if there's a splitter connected to the modem?

Regular Visitor

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4 Messages

Thanks for the reply.

All connections are tight.  There is one splitter between the service entrance and the modem.  It's labeled as CommScope SV-2G.  Nothing has changed with any parts or cabling.

Thanks again

Official Employee

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1K Messages

Thanks for letting us know this information, DT_UM. Let's take a closer look and see what is going on. 

 

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Expert

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107.2K Messages

@XfinityWilliam​ 

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Expert

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107.2K Messages

2 months ago

@DT_UM 

First. You'll never be able to get your subscribed to speeds with that modem. Comcast rates it to 845 Mbps;

https://www.xfinity.com/support/devices#details

Second. This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless. First. 

The upstream power is on the high side and it may be intermittently fluctuating even higher to out of spec levels. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

In an effort to try to obtain better connectivity / more wiggle room, check to see if there are any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage from Home Depot, Target, Wal-Mart, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, abrasions, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.


Good luck with it !

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