U

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10 Messages

Thursday, October 27th, 2022 6:03 PM

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new modem needed?

I have an arris SB6183 and the 400Mbps plan. I used the modem with little to no problems for the last two years (bought it new), then recently started having problems after I moved. I get random packet delay/drops (once every 5ish min) and occasional modem resets (1-3 times daily that I've noticed). My speeds are also much slower than I'd expect, never surpassing 100Mbps. I wanted to get someone out here to check the downstream power levels as they sit around 9ish dBmV (close to the spec limit) and I have read that high power levels can cause some issues that I have experienced, but the tech on the phone told me the issue was that my modem is old and I need a new one, does this sound right? This modem is still being sold in stores today, so it seems odd to me. My modem logs are also absolutely full of critical alerts, can post if they'd be helpful.

Note: I know that 400 is pushing the capabilities of the modem I have, I am more than fine with only getting 300ish due to the modem. Perhaps that could be causing the slow speeds, but I don't see how it would be causing the resets and packet loss.

Accepted Solution

Visitor

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10 Messages

3 months ago

Updating this now the the issues I've had are resolved:

Tech came out a week and a half ago and removed what he called a 'filter' that was connected to my line at the pole. Said it doesn't cause issues for Xfinity modems so that's how it can go unnoticed, but it shouldn't have been on there. Since then it has worked much better, I have only gotten a few modem errors in the last week or so as opposed to dozens every hour (with occasional modem reset) and no longer have huge ping spikes when gaming.

Glad it has been fixed, a little peeved at the process because different representatives on the phone told me different things with the same info. One told me that their readings indicated a connection issue while another told me it was certainly my modem (obviously incorrect in retrospect). Without my own research and the help of people on here I would not have had the knowledge to be confident and persistent in getting a tech out here rather than replacing my equipment.

Also, since the fix the modem now has multiple upstream channels, so definitely was a connection issue there

(edited)

zip21222

Contributor

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154 Messages

3 months ago

@user_93f883 

Yes, technically using a modem that is not approved for your speed tier can cause a host of problems.

But please, please take a quick browse thru this forum and see just how many people are in your position, ie they move, comcast tells em they need new gear, they get one, two, sometimes three new modems, and yet their problems remain.

Sadly it's a very difficult position to be in. Comcast won't even begin to troubleshoot until you get an approved modem, and then every time your service fails to improve they will say your new modem is defective, and you really need to rent a gateway from them.

Sorry to be such a party pooper, but the more time I spend in these forums the sadder it makes me.

On the up side, there are some very helpful folks here, so posting your up and downstream levels plus your logs, might get you the help you need.

Please make sure you redact MAC & IP addresses from the logs.

HTH

Visitor

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10 Messages

3 months ago

@zip21222​ Thanks for the response. I was/am worried about them giving me the equipment runaround. The phone tech actually cancelled a service appointment I had scheduled, which is annoying since them coming out would have helped attacked the problem from multiple angles. I was hoping that I wouldn't have any issues because Comcast is my only provider for the area, and ISPs are notoriously painful to work with (especially when not renting their equipment), but wasn't so lucky.

Power Levels & other info (at this moment the levels are lower but I have seen them as high as 9.3):

Channel Lock Status Modulation Channel ID Frequency Power SNR Corrected Uncorrectables
1 Locked QAM256 4 417000000 Hz 8.1 dBmV 39.5 dB 0 0
2 Locked QAM256 1 399000000 Hz 7.8 dBmV 39.6 dB 0 0
3 Locked QAM256 2 405000000 Hz 8.0 dBmV 39.6 dB 0 0
4 Locked QAM256 3 411000000 Hz 8.0 dBmV 39.6 dB 0 0
5 Locked QAM256 5 423000000 Hz 8.1 dBmV 39.5 dB 0 0
6 Locked QAM256 6 429000000 Hz 8.2 dBmV 39.5 dB 0 0
7 Locked QAM256 7 435000000 Hz 8.1 dBmV 39.4 dB 0 0
8 Locked QAM256 8 441000000 Hz 8.1 dBmV 39.4 dB 0 0
9 Locked QAM256 9 447000000 Hz 8.2 dBmV 39.3 dB 0 0
10 Locked QAM256 10 453000000 Hz 8.3 dBmV 39.3 dB 0 0
11 Locked QAM256 11 459000000 Hz 8.5 dBmV 39.3 dB 0 0
12 Locked QAM256 12 465000000 Hz 8.5 dBmV 39.2 dB 0 0
13 Locked QAM256 13 471000000 Hz 8.7 dBmV 39.2 dB 0 0
14 Locked QAM256 14 477000000 Hz 8.7 dBmV 39.1 dB 0 0
15 Locked QAM256 15 483000000 Hz 8.9 dBmV 39.1 dB 0 0
16 Locked QAM256 16 489000000 Hz 8.9 dBmV 39.1 dB 0 0

Logs snippet (there is much more, seems to be a set of errors every 10 minutes or so:

Wed Oct 26 22:22:03 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out
Wed Oct 26 22:22:33 2022 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Wed Oct 26 22:32:52 2022 Critical (3) No Ranging Response received - T3 time-out
Wed Oct 26 22:33:02 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
Wed Oct 26 22:33:32 2022 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Wed Oct 26 22:43:49 2022 Critical (3) No Ranging Response received - T3 time-out
Wed Oct 26 22:43:59 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
Wed Oct 26 22:44:25 2022 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out
Wed Oct 26 22:54:45 2022 Critical (3) No Ranging Response received - T3 time-out
Wed Oct 26 22:54:46 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
Wed Oct 26 22:54:46 2022 Critical (3) No Ranging Response received - T3 time-out
Wed Oct 26 22:54:57 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
zip21222

Contributor

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154 Messages

3 months ago

@user_93f883 

[sigh] was in almost your exact situation a couple years ago, so I know...

first, could you post your upstream numbers also? Need to see both sides.

The downstream power levels are on the high side, but in-spec, the SNRs are in-spec, and zero correcteds and uncorrecteds is a good sign.

I'm far from a docsis expert, but those log entries don't look (to me at least) like the kinda stuff that would cause your problems.

I don't see any disconnects or restarts, which are the most common red flags (to me).

Let's see what, if anything, the upstream numbers tell us.

HTH

EG

Expert

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97.6K Messages

@zip21222​ wrote;

I'm far from a docsis expert, but those log entries don't look (to me at least) like the kinda stuff that would cause your problems.

They certainly can. The OP @user_93f883 stated this: " and occasional modem resets (1-3 times daily that I've noticed)."

Some info on modem RF errors;

https://pickmymodem.com/cable-modem-t3-and-t4-timeouts-error-messages-and-how-to-fix-them/ 

(edited)

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Visitor

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10 Messages

@EG 

Thanks for the link. If I'm seeing that right, I probably have to call and ask for a tech again to fix this, because I am getting lots of T3 and T2 errors in my logs

EDIT: unless the modem not being rated for this speed tier is what causes these problems, I have no idea if that is something that could happen

(edited)

EG

Expert

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97.6K Messages

@user_93f883​ wrote;

 EDIT:  "because I am getting lots of T3 and T2 errors in my logs" and "unless the modem not being rated for this speed tier is what causes these problems"

The speed rating issue can not cause T errors. They are RF / impairment / connection quality based.

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Visitor

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10 Messages

@EG 

Good to know, thanks. I will call comcast and insist on getting some help then before I buy a new modem. One thing I think might be causing it is that I moved the line coming into my house (used to go all the way around the exterior, changed it to go right into the basement) which left me with like 15 extra feet of cable that I coiled up. I'm weak on my RF but I know coils are dangerous in this respect.

Visitor

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10 Messages

3 months ago

gotcha, here is my upstream:

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 4 5120 Ksym/sec 35600000 Hz 45.0 dBmV



zip21222

Contributor

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154 Messages

3 months ago

@user_93f883 

well, everything's to spec technically.

the first thing I'd do is check for plant issues (cables, splitters,etc) in any spaces that are accessible to you.

Take a look at the pinned 'Internet Troubleshooting Tips' topic in this forum, in particular the section from 'Inspect cabling' down to 'Check the quality/status of all splitters'.

If you don't find anything, you could try a forward path attenuator to lower your downstream power without negatively effecting upstream power.

This is the one I use.

HTH

Visitor

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10 Messages

3 months ago

@zip21222 

Thanks for the pointers. I will check out that topic

As for the cable checking, the coax cable goes directly from the comcast box to my modem, no splitters or other such connections.

I will probably check out an attenuator if nothing else crops up, as that would be far less expensive than getting a new modem.

BruceW

Gold Problem Solver

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24.4K Messages

3 months ago

... SB6183 ... I know that 400 is pushing the capabilities of the modem I have ...

You're not "pushing the capabilities", you're trying to use a modem on a speed tier for which it is not approved. https://www.xfinity.com/support/devices says the SB6183 is approved for use with plan speeds "Up to 373 Mbps". Using devices on Internet speed tiers for which Comcast has not approved them tends to produce unexpected results, often speeds well below the manufacturer's ratings. It would be best to upgrade the device, or to choose a lower plan speed for which the device is approved.

...  here is my upstream ...

Something's wrong here. There should be at least 3 upstream channels locked. The drop at your new location may require attention.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

(edited)

zip21222

Contributor

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154 Messages

@BruceW​ 

Not trying to be a jerk or anything, but this is a screenshot of the SB8200 I'm working from a few minutes ago:

EG

Expert

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97.6K Messages

Apparently you have a problem too. BruceW was correct. Comcast currently provides 3 to 6 upstream channels.

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zip21222

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154 Messages

@EG 

The count bounces around all day. I assumed it had to do with how much bandwidth I'm using. Sometimes it's one, sometimes it's three, sometimes it's four.

If I do a speedtest it's almost always four afterwards.

Connection's been solid for months now. (fingers crossed){grin}

EG

Expert

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97.6K Messages

@zip21222​ 

That's a connection quality problem. It's not related to bandwidth consumption or anything else.

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I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

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Visitor

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10 Messages

3 months ago

@BruceW 

Thanks for the info, I have been trying to get onto that page you linked all day but it never finishes loading for me (have tried on my network and mobile data) to see the info for my modem. I am surprised by this as the manufacturer rates it for 600, so not even being able to take 2/3 the rated is rather disappointing.

As for the upstream, double checked my modem page to be sure and yup, there is only one upstream. Not sure how concerned I should be about it. Seems like it'd be pulling teeth to get a tech out for that.

Also, it seems the logs and my packet issues may be linked. Here is a log output and ping test output where the critical errors seem to coincide with an instance of extremely high ping (modem timestamp is an hour behind)

I haven't been actively cross referencing these, so I will keep watching to see if there is a pattern

Log:

Thu Oct 27 15:52:53 2022 Critical (3) No Ranging Response received - T3 time-out
Thu Oct 27 15:53:03 2022 Critical (3) No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;
Thu Oct 27 15:53:08 2022 Warning (5) Dynamic Range Window violation
Thu Oct 27 15:53:33 2022 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;

Ping:

10/27/2022 4:53:04 PM - Reply from 8.8.8.8: bytes=32 time=18ms TTL=56
10/27/2022 4:53:05 PM - Reply from 8.8.8.8: bytes=32 time=19ms TTL=56
10/27/2022 4:53:06 PM - Reply from 8.8.8.8: bytes=32 time=18ms TTL=56
10/27/2022 4:53:07 PM - Reply from 8.8.8.8: bytes=32 time=17ms TTL=56
10/27/2022 4:53:08 PM - Reply from 8.8.8.8: bytes=32 time=20ms TTL=56
10/27/2022 4:53:11 PM - Reply from 8.8.8.8: bytes=32 time=1798ms TTL=56
10/27/2022 4:53:11 PM - Reply from 8.8.8.8: bytes=32 time=19ms TTL=56
10/27/2022 4:53:12 PM - Reply from 8.8.8.8: bytes=32 time=18ms TTL=56
10/27/2022 4:53:13 PM - Reply from 8.8.8.8: bytes=32 time=21ms TTL=56
10/27/2022 4:53:14 PM - Reply from 8.8.8.8: bytes=32 time=19ms TTL=56
10/27/2022 4:53:15 PM - Reply from 8.8.8.8: bytes=32 time=39ms TTL=56

EDIT: Just got another laggy packet and yup, there is a corresponding error log

EDIT 2: Now have 4 logs and 4 laggy packets that correspond to each other

(edited)

Visitor

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10 Messages

3 months ago

UPDATE: Sometime during my troubleshooting my internet speed drastically improved (from 90ish mbps to 400ish) but the packet issue remains. This makes me think that it is a comcast problem rather than my modem, as even after reverting to my original network setup/configuration the higher speed remains.

XfinityJorge

Official Employee

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604 Messages

Hello @user_93f883 thank you so much for contacting our Xfinity Support Team over our Forums. You came to the right place for help, and we are happy to look into your connection, so we can help with the internet issues that still remain. In order to get started, can you please send me a private message to Xfinity Support with your full name and full address by clicking the chat icon in the top right?

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zip21222

Contributor

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154 Messages

3 months ago

Awesome!!

Crossing my fingers that it stays that way!

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