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New Modem for Gigabit Internet, not getting correct speeds

Contributor

New Modem for Gigabit Internet, not getting correct speeds

Good Morning,

Last night I purchased and installed/activated a new modem (Netgear CM1000) in order to take advantage of Docsis 3.1 and the gigabit internet that I am subscribed too.  However I am not getting over 500Mbps down when wired directly to the modem.  As well it is only using 24 out of 32 bonded downstream channels and 3 of 8 upstream.  It is only using 1 of 2 OFDM downstream channels and 0 of 2 upstream OFDMA channels.

 

My modem info is:

Hardware version: 2.02

Fireware version: 3.01.04

Downstream Bonded Channels

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

SNR / MER

Unerrored Codewords

Correctable Codewords

Uncorrectable Codewords

1

Locked

QAM256

21

627000000 Hz

0.8 dBmV

41.3 dB

2497308915

0

0

2

Locked

QAM256

1

507000000 Hz

1.5 dBmV

42.1 dB

2494793920

0

0

3

Locked

QAM256

2

513000000 Hz

1.5 dBmV

42.1 dB

2494803418

0

0

4

Locked

QAM256

3

519000000 Hz

1.4 dBmV

41.8 dB

2494812334

0

0

5

Locked

QAM256

4

525000000 Hz

1.2 dBmV

41.9 dB

2494821629

0

0

6

Locked

QAM256

5

531000000 Hz

1.2 dBmV

42.0 dB

2494831504

0

0

7

Locked

QAM256

6

537000000 Hz

1.2 dBmV

42.1 dB

2494840242

0

0

8

Locked

QAM256

7

543000000 Hz

1.0 dBmV

42.1 dB

2494850220

0

0

9

Locked

QAM256

8

549000000 Hz

1.1 dBmV

42.3 dB

2494861695

0

0

10

Locked

QAM256

9

555000000 Hz

1.0 dBmV

42.2 dB

2494870681

0

0

11

Locked

QAM256

10

561000000 Hz

1.2 dBmV

42.2 dB

2494879928

0

0

12

Locked

QAM256

11

567000000 Hz

1.2 dBmV

42.1 dB

2494889260

0

0

13

Locked

QAM256

12

573000000 Hz

1.4 dBmV

42.2 dB

2494899254

0

0

14

Locked

QAM256

13

579000000 Hz

1.3 dBmV

42.2 dB

2494907315

0

0

15

Locked

QAM256

14

585000000 Hz

1.5 dBmV

42.0 dB

2494916544

0

0

16

Locked

QAM256

15

591000000 Hz

1.4 dBmV

42.0 dB

2494926642

0

0

17

Locked

QAM256

16

597000000 Hz

1.6 dBmV

41.8 dB

2494935578

0

0

18

Locked

QAM256

17

603000000 Hz

1.4 dBmV

41.8 dB

2494944755

0

0

19

Locked

QAM256

18

609000000 Hz

1.4 dBmV

41.8 dB

2494954283

0

0

20

Locked

QAM256

19

615000000 Hz

1.1 dBmV

41.7 dB

2494964052

0

0

21

Locked

QAM256

20

621000000 Hz

1.2 dBmV

41.6 dB

2494972988

0

0

22

Locked

QAM256

22

633000000 Hz

0.9 dBmV

41.5 dB

2494982167

0

0

23

Locked

QAM256

23

639000000 Hz

0.6 dBmV

41.3 dB

2494989101

0

0

24

Locked

QAM256

24

645000000 Hz

0.9 dBmV

41.2 dB

2494996061

0

0

25

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

26

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

27

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

28

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

29

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

30

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

31

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

32

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

 

Upstream Bonded Channels

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

1

Locked

ATDMA

1

36500000 Hz

50.0 dBmV

2

Locked

ATDMA

2

30100000 Hz

50.0 dBmV

3

Locked

ATDMA

3

23700000 Hz

49.0 dBmV

4

Not Locked

Unknown

0

0 Hz

0.0 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

 

Downstream OFDM Channels

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, 1

159

678000000 Hz

1.5 dBmV

40.0 dB

1126 ~ 2969

2129179380

14107044

0

2

Not Locked

0

0

0 Hz

0.7 dBmV

0.0 dB

0 ~ 4095

0

0

0

 

Upstream OFDMA Channels

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

 

Thank you

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds


wrote:

It is only using 1 of 2 OFDM downstream channels and 0 of 2 upstream OFDMA channels.


FWIW, Comcast currently offers only one OFDM / D3.1 downstream carrier. Only one is needed for gigabit. And that carrier is indeed being utilized for data transmission as it is showing bit errors. Also, many areas still offer only 3 upstream carriers.

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

Did not know that about the downstream d3.1. 

Shouldn't I be utilizing more than 24 downstream channels though?  As well could the speed issue be from an incorrect boot file or could there be issues elsewhere?

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

Although data may be carried by both the D3.0 and the D3.1 OFDM downstream channels (depending on the local system / equipment), the OFDM channel's bandwidth capability is all that is really needed. Many systems are now configured for only 24 D3.0 channels and one OFDM D3.1 channel.

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

Could it be something else entirely then that's causing me to only get 50% of the speed?

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

I don't think that this is related to or is the root cause of the problem but I will also tell you that the upstream power is borderline / too high and may be intermittently fluctuating even higher out of spec. That can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there 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 types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

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.


Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

We have been experiencing modem reboots every few days, that's why we decided to up our internet and get a new modem.  However we had similar problems last year, and they sent techs out.  Those techs were supposed to have taken the coax directly from the street into where the modem sits.  We only have internet so we only need the one coax cable.  I will take a look and see if it's dirty or anything tonight.

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

I gave it a few days to see if that would help at all, but it hasn't.  I took a look at our cabling, and I was right. The line comes from the street to an extender which then goes directly into the wall where the modem is.  It is also clean, and looks new.  I'm now getting these results from my modem:

 

Frequency start Value

This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.

Starting Frequency

627000000

 

Startup Procedure

Procedure

Status

Comment

Acquire Downstream Channel

627000000 Hz

Locked

Connectivity State

OK

Operational

Boot State

OK

Operational

Security

Enable

BPI+

IP Provisioning Mode

Honor MDD

IPv6 only

 

Downstream Bonded Channels

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

SNR / MER

Unerrored Codewords

Correctable Codewords

Uncorrectable Codewords

1

Locked

QAM256

21

627000000 Hz

2.6 dBmV

41.3 dB

1029926369

177

230

2

Locked

QAM256

1

507000000 Hz

3.3 dBmV

41.8 dB

1027813075

406

279

3

Locked

QAM256

2

513000000 Hz

3.3 dBmV

41.9 dB

1027821599

316

344

4

Locked

QAM256

3

519000000 Hz

3.1 dBmV

41.9 dB

1027831373

352

261

5

Locked

QAM256

4

525000000 Hz

2.9 dBmV

41.8 dB

1027838224

359

274

6

Locked

QAM256

5

531000000 Hz

3.0 dBmV

41.9 dB

1027849408

342

296

7

Locked

QAM256

6

537000000 Hz

3.0 dBmV

41.8 dB

1027857885

321

242

8

Locked

QAM256

7

543000000 Hz

2.8 dBmV

42.2 dB

1027868187

351

233

9

Locked

QAM256

8

549000000 Hz

2.8 dBmV

42.1 dB

1027935964

414

290

10

Locked

QAM256

9

555000000 Hz

2.8 dBmV

41.6 dB

1027944449

333

285

11

Locked

QAM256

10

561000000 Hz

3.0 dBmV

41.8 dB

1027954905

323

244

12

Locked

QAM256

11

567000000 Hz

3.1 dBmV

42.1 dB

1027964072

291

255

13

Locked

QAM256

12

573000000 Hz

3.1 dBmV

42.1 dB

1027974389

358

199

14

Locked

QAM256

13

579000000 Hz

3.1 dBmV

42.0 dB

1027982027

256

246

15

Locked

QAM256

14

585000000 Hz

3.3 dBmV

41.9 dB

1027991557

257

267

16

Locked

QAM256

15

591000000 Hz

3.2 dBmV

41.9 dB

1028001744

244

244

17

Locked

QAM256

16

597000000 Hz

3.3 dBmV

41.8 dB

1028010165

207

247

18

Locked

QAM256

17

603000000 Hz

3.2 dBmV

41.6 dB

1028020246

233

214

19

Locked

QAM256

18

609000000 Hz

3.2 dBmV

41.6 dB

1028029213

228

195

20

Locked

QAM256

19

615000000 Hz

2.9 dBmV

41.6 dB

1028038641

208

207

21

Locked

QAM256

20

621000000 Hz

2.9 dBmV

41.5 dB

1028048425

191

188

22

Locked

QAM256

22

633000000 Hz

2.6 dBmV

41.4 dB

1028056883

190

211

23

Locked

QAM256

23

639000000 Hz

2.5 dBmV

41.3 dB

1028064798

180

173

24

Locked

QAM256

24

645000000 Hz

2.6 dBmV

41.3 dB

1028070816

163

207

25

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

26

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

27

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

28

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

29

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

30

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

31

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

32

Not Locked

Unknown

0

0 Hz

0.0 dBmV

0.0 dB

0

0

0

 

Upstream Bonded Channels

Channel

Lock Status

Modulation

Channel ID

Frequency

Power

1

Locked

ATDMA

1

36500000 Hz

49.0 dBmV

2

Locked

ATDMA

2

30100000 Hz

49.0 dBmV

3

Locked

ATDMA

3

23700000 Hz

48.5 dBmV

4

Not Locked

Unknown

0

0 Hz

0.0 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

 

Downstream OFDM Channels

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, 1

159

678000000 Hz

3.4 dBmV

40.0 dB

1126 ~ 2969

16609763238

200969140

4

2

Not Locked

0

0

0 Hz

2.5 dBmV

0.0 dB

0 ~ 4095

0

0

0

 

Upstream OFDMA Channels

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

 

 

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

There is still not much wiggle room on the upstream power. A goal would have it to be 40 dB to 45 dB.

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

Interesting, because my upload speeds are much higher than they should be.

Do my downstream numbers look ok?
Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

Yes. The downstream is o/k. Even though the upstream power is close to being too high, apparently it is not yet so high as to affect your upload speed, but it is a problem just waiting to happen (mostly with disconnects and spontaneous modem re-booting). In the Summertime the number can go higher by as much as 3-4 dB. That's why I state "not much wiggle room".

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

So on Sunday I returned my Netgear CM1000 for an Arris SB8200. There were a lot of problems getting the modem initially activated and since then we have not gotten the speeds we are paying for.  We are getting even less than what we got with the Netgear.  The speeds we are getting are the same as our old Blast! speeds.  I attached the Status page and the Event log.  I notice that there isn't a separate section for Docsis 3.1 as well and I think our Gigabit channel isn't functioning.

 

Time Priority Description
3-12-2018, 14:12:17 Warning(5) "Dynamic Range Window violation"
1-1-1970, 0:0:43 Notice(6) "Honoring MDD; IP provisioning mode = IPv6"
1-1-1970, 0:0:33 Critical(3) "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
3-10-2018, 14:32:11 Critical(3) "Resetting the cable modem due to docsDevResetNow"
1-1-1970, 0:0:33 Critical(3) "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:2:9 Critical(3) "No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:1:58 Critical(3) "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:29 Critical(3) "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
1-1-1970, 0:0:33 Critical(3) "Telnet user logged in from IP address 192.168.100.10."
1-1-1970, 0:0:28 Critical(3) "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"

 

Downstream Bonded Channels
Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
21 Locked QAM256 627000000 Hz 2.8 dBmV 40.3 dB 211 1
1 Locked QAM256 507000000 Hz 2.6 dBmV 40.8 dB 241 182
2 Locked QAM256 513000000 Hz 2.7 dBmV 40.8 dB 259 203
3 Locked QAM256 519000000 Hz 2.9 dBmV 40.8 dB 232 143
4 Locked QAM256 525000000 Hz 2.7 dBmV 40.4 dB 333 90
5 Locked QAM256 531000000 Hz 3.0 dBmV 40.7 dB 305 72
6 Locked QAM256 537000000 Hz 3.0 dBmV 40.8 dB 273 85
7 Locked QAM256 543000000 Hz 3.2 dBmV 40.8 dB 284 115
8 Locked QAM256 549000000 Hz 3.4 dBmV 40.8 dB 190 110
9 Locked QAM256 555000000 Hz 3.7 dBmV 40.8 dB 295 43
10 Locked QAM256 561000000 Hz 3.9 dBmV 40.9 dB 297 21
11 Locked QAM256 567000000 Hz 4.2 dBmV 40.9 dB 260 24
12 Locked QAM256 573000000 Hz 4.3 dBmV 40.9 dB 171 55
13 Locked QAM256 579000000 Hz 4.6 dBmV 40.9 dB 218 50
14 Locked QAM256 585000000 Hz 4.5 dBmV 40.8 dB 186 41
15 Locked QAM256 591000000 Hz 4.5 dBmV 40.8 dB 230 29
16 Locked QAM256 597000000 Hz 4.2 dBmV 40.7 dB 227 2
17 Locked QAM256 603000000 Hz 4.1 dBmV 40.7 dB 173 0
18 Locked QAM256 609000000 Hz 3.8 dBmV 40.6 dB 171 0
19 Locked QAM256 615000000 Hz 3.6 dBmV 40.5 dB 215 0
20 Locked QAM256 621000000 Hz 3.3 dBmV 40.4 dB 157 31
22 Locked QAM256 633000000 Hz 2.6 dBmV 40.1 dB 167 0
23 Locked QAM256 639000000 Hz 2.4 dBmV 40.2 dB 115 0
24 Locked QAM256 645000000 Hz 2.3 dBmV 40.1 dB 134 0
159 Locked Other 678000000 Hz 3.8 dBmV 38.8 dB 17582486 1

 

 
Upstream Bonded Channels
Channel Channel ID Lock Status US Channel Type Frequency Width Power
1 3 Locked SC-QAM 23700000 Hz 6400000 Hz 45.5 dBmV
2 1 Locked SC-QAM 36500000 Hz 6400000 Hz 46.0 dBmV
3 2 Locked SC-QAM 30100000 Hz 6400000 Hz

45.5 dBmV

Problem Solver

Re: New Modem for Gigabit Internet, not getting correct speeds

FYI, the channel ID 159 you see with the “Other” after is the OFDM channel.
Expert

Re: New Modem for Gigabit Internet, not getting correct speeds


@apnowak91 wrote:

and I think our Gigabit channel isn't functioning.


FWIW, there are corrected bit errors there so the OFDM carrier is indeed "functioning";

 

159 Locked Other 678000000 Hz 3.8 dBmV 38.8 dB 17582486 1
Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

That's good to know, but I still don't understand why we are getting even slower speeds as before. And it's a consistent speed.  ~250Mbps.

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

What are you getting for the upload speed ?

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

Between 35 and 50. Lowest is usually 35. Hovers around 40 for the most part. So I know something is going right because the upload speed is normal.

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

Yep. Don't know what the issue is but it doesn't appear to be with the provisioning / boot file. It may be the CMTS firmware glitch with the OFDM channel that we've been seeing here.

Contributor

Re: New Modem for Gigabit Internet, not getting correct speeds

I assume it's a known glitch that will be fixed in an upcoming update?

Expert

Re: New Modem for Gigabit Internet, not getting correct speeds

I'm not a CC employee but I've seen posts from an Arris engineer who frequents the boards here indicating that it is a known issue and is being addressed.

Regular Visitor

Re: New Modem for Gigabit Internet, not getting correct speeds

I am in exactly same boat as you only I started with SB8200 and swapped for CM1000. Getting low 200s down and 40 up. Tried to plugin at the drop off point no change. Getting a tech to come out to look at it. Btw, what is your status now? Were you able to fix this? Thanks!

New Poster

Re: New Modem for Gigabit Internet, not getting correct speeds

I'm having the same issue as well. Recently switched out my Arris TG862G for the CM1000 and upgraded to Gigabit. Seeing around Blast! D/L speeds but around 40 up. Had a tech out yesterday and he was stumped because all the levels look good. There was some question early on about a missing bootfile but I can see it in the modem config. They reprovisioned to no avail. There are coming out again today to keep looking. Will keep you posted.

Official Employee

Re: New Modem for Gigabit Internet, not getting correct speeds

 

Hello badamonis, I can assist you with getting your speeds back up to normal. Please send me a private message with your full name, street address, and account number by clicking on my name (ComcastAmir) and then "private message me" and we can get started on checking your signals and modem health. 

Problem Solver

Re: New Modem for Gigabit Internet, not getting correct speeds

@badamonis and @DT_CT

 

If after reprovisiong doesnt help, try a factory reset of the modem by pressing in and holding the reset button on the back of the modem for 30-60 seconds and see how that goes.