residential cable modem and business cable modem both on same coax?
Hello,
I'd like to know if it's acceptable to have both cable modems connected to the same main coax cable? Our internet went out today out of the blue, and I tracked it back to a bad cable splitter that the installer put in when they added my wifes business internet for her home office. I was under the impression that this was an invalid setup, causes signal interference, and other issues, but I'm not a pro so didn't push back on it at the time. We have been unsatisfied with our internet performance, when it works, it's good and very fast. But it frequently has outages and disconnects for 10-15 seconds multiple times/day. Even now after changing the spliter I still see warnings in the event log, and wondering if this is the cause or something else.
REG-RSP-MP Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;
Cable Connection
Cancel Apply
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
Startup Procedure
Procedure
Status
Comment
Acquire Downstream Channel
531000000 Hz
Locked
Connectivity State
OK
Operational
Boot State
OK
Operational
Security
Enabled
BPI+
Downstream Bonded Channels
Channel
Lock Status
Modulation
Channel ID
Frequency
Power
SNR
Correctables
Uncorrectables
1
Locked
QAM256
21
531000000 Hz
7.6 dBmV
42.5 dB
0
0
2
Locked
QAM256
13
477000000 Hz
6.7 dBmV
42.3 dB
0
0
3
Locked
QAM256
14
483000000 Hz
6.7 dBmV
42.3 dB
0
0
4
Locked
QAM256
15
489000000 Hz
6.8 dBmV
42.3 dB
1
0
5
Locked
QAM256
16
495000000 Hz
6.7 dBmV
42.3 dB
0
0
6
Locked
QAM256
17
507000000 Hz
6.9 dBmV
42.3 dB
0
0
7
Locked
QAM256
18
513000000 Hz
7.0 dBmV
42.3 dB
0
0
8
Locked
QAM256
19
519000000 Hz
7.1 dBmV
42.4 dB
0
0
9
Locked
QAM256
20
525000000 Hz
7.4 dBmV
42.4 dB
0
0
10
Locked
QAM256
22
537000000 Hz
7.8 dBmV
42.6 dB
1
0
11
Locked
QAM256
23
543000000 Hz
7.9 dBmV
42.6 dB
0
0
12
Locked
QAM256
24
549000000 Hz
7.8 dBmV
42.5 dB
0
0
13
Locked
QAM256
25
555000000 Hz
7.6 dBmV
42.4 dB
0
0
14
Locked
QAM256
26
561000000 Hz
7.7 dBmV
42.5 dB
0
0
15
Locked
QAM256
27
567000000 Hz
7.7 dBmV
42.5 dB
0
0
16
Locked
QAM256
28
573000000 Hz
7.7 dBmV
42.4 dB
2
0
17
Locked
QAM256
29
579000000 Hz
7.8 dBmV
42.4 dB
0
0
18
Locked
QAM256
30
585000000 Hz
8.0 dBmV
42.5 dB
0
0
19
Locked
QAM256
31
591000000 Hz
8.2 dBmV
42.6 dB
0
0
20
Locked
QAM256
32
597000000 Hz
8.4 dBmV
42.6 dB
0
0
21
Locked
QAM256
33
603000000 Hz
8.4 dBmV
42.6 dB
2
0
22
Locked
QAM256
34
609000000 Hz
8.5 dBmV
42.7 dB
1
0
23
Locked
QAM256
35
615000000 Hz
8.5 dBmV
42.6 dB
0
0
24
Locked
QAM256
36
621000000 Hz
8.2 dBmV
42.6 dB
1
0
25
Locked
QAM256
37
627000000 Hz
8.0 dBmV
42.5 dB
1
0
26
Locked
QAM256
38
633000000 Hz
7.8 dBmV
42.4 dB
0
0
27
Locked
QAM256
39
639000000 Hz
7.4 dBmV
42.2 dB
0
0
28
Locked
QAM256
40
645000000 Hz
7.0 dBmV
42.1 dB
0
0
29
Locked
QAM256
41
651000000 Hz
6.7 dBmV
42.0 dB
1
0
30
Locked
QAM256
42
657000000 Hz
6.6 dBmV
42.0 dB
0
0
31
Locked
QAM256
43
663000000 Hz
6.5 dBmV
41.9 dB
0
0
32
Locked
QAM256
44
669000000 Hz
6.7 dBmV
42.0 dB
2
0
Upstream Bonded Channels
Channel
Lock Status
US Channel Type
Channel ID
Symbol Rate
Frequency
Power
1
Locked
ATDMA
2
5120
16400000 Hz
57.3 dBmV
2
Locked
ATDMA
3
5120
22800000 Hz
57.8 dBmV
3
Locked
ATDMA
4
5120
29200000 Hz
58.3 dBmV
4
Locked
ATDMA
5
5120
35600000 Hz
58.8 dBmV
5
Not Locked
Unknown
0
0
0 Hz
0.0 dBmV
6
Not Locked
Unknown
0
0
0 Hz
0.0 dBmV
7
Not Locked
Unknown
0
0
0 Hz
0.0 dBmV
8
Not Locked
Unknown
0
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
159
678000000 Hz
7.7 dBmV
41.9 dB
1126 ~ 2969
61210990
109683
0
2
Not Locked
0
0
0 Hz
0 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
0
0
0 Hz
0 dBmV
2
Not Locked
0
0
0 Hz
0 dBmV
Extended Upstream Transmit Power
Current System Time:Sat Jan 08 16:53:49 2022
System Up Time:00:27:05
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Specs look great now. The uncorrectables may be due to the linework that was done. You can reboot the modem to reset the error counter and start from scratch. Keep an eye on the amount of them, and whether they happen quickly or over a longer length of time. The bottom line is if the connection is now more stable. Good luck !
thank you so much for all of your help. you are right, after 1/2 hour, no uncorrectables. I believe my issues are solved, only time will tell if the drops are done, but we can call this closed. thanks again
thank you so much for all of your help. you are right, after 1/2 hour, no uncorrectables. I believe my issues are solved, only time will tell if the drops are done, but we can call this closed. thanks again
You're welcome but I'd give it at least 24 to 48 hours and see. Hope things hold up for you ! Good luck !
I am not a Comcast Employee. 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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The upstream power is WAY out of spec !!! 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 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 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, 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, 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.
@EG That's the only splitter in the whole house, one leg goes to our cable modem, the other goes to wife's employer's cable modem. We only have internet so no other devices besides the 2 cable modems, and no other coax besides those 3 lines (counting the feed). I had already checked the 3 connections for corrosion and tightness when I was troubleshooting before. The splitter (Antronix CMC2002H-A 5-100Mhz 2 way) may be poor quality I don't really know, it's the only one I had on hand after finding the Extreme BDS108H the installer put in is no longer functioning about an hour ago. I'm waiting for an Extreme BDS102H to show up in the mail, already ordered, when it arrives I'll swap it out and check again. Can you tell me what the upstream power range should be? I think it might be worthwhile to swap out the coax between the modem and the splitter also. I don't see an RG value on it, it only says perfectflex series 6 18awg.
The Antronix is a very good quality splitter that Comcast uses widely, but it may be malfunctioning. Only a swap would rule that out.
That's RG6 which is the preferred cable. But it may not be *quad shield* which may be better depending on the length of the run. But it's also more difficult (stiffer) to work with.
40 to 50 dB is the preferred range with 45 being the *sweet spot*.
So if there is nothing that you can do to improve the connection quality, then you should get a tech out to investigate / correct the problem as stated.
Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.
Note: Not all modems will allow you to view the status page and some will have different URLs to access this info. If you are unable to access your modem’s status page, you can contact Comcast Customer Support and ask the support representative for these values.
@EG I removed the splitter and connected the cable modem directly to the drop from the pole, and get even more errors in the log. I don't want to waste your time, I'm escalating to Comcast, just wanted to get this additional info out there in case it changes your advice in any way
DBC-REQ Mismatch Between Calculated Value for P1.6hi Compared to CCAP Provided Value;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Mon Jan 10 14:39:55 2022
(Critical (3))
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=[Edited: "Personal Information"];CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Downstream power is now out of spec, too high. Upstream power is lower, but still over 50
Cable Connection
Cancel Apply
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.
@EG thanks for your help. Tech came out today and guessed the symptoms before I even had a chance to explain. He found and a filter, and removed it, but power was still out of spec. He escalated to another team who showed up an hour or 2 later. Power levels are in spec now based on the guideline you shared earlier. I now have uncorrectables, but I'm guessing that doesn't mean much by itself if we don't have other issues going forward?
Cable Connection
Cancel Apply
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.
Accepted Solution
EG
Expert
•
111.4K Messages
3 years ago
Specs look great now. The uncorrectables may be due to the linework that was done. You can reboot the modem to reset the error counter and start from scratch. Keep an eye on the amount of them, and whether they happen quickly or over a longer length of time. The bottom line is if the connection is now more stable. Good luck !
2
0
EG
Expert
•
111.4K Messages
3 years ago
The upstream power is WAY out of spec !!! 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 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 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, 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, 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 !
(edited)
1
0
EG
Expert
•
111.4K Messages
3 years ago
The Antronix is a very good quality splitter that Comcast uses widely, but it may be malfunctioning. Only a swap would rule that out.
That's RG6 which is the preferred cable. But it may not be *quad shield* which may be better depending on the length of the run. But it's also more difficult (stiffer) to work with.
40 to 50 dB is the preferred range with 45 being the *sweet spot*.
So if there is nothing that you can do to improve the connection quality, then you should get a tech out to investigate / correct the problem as stated.
Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.
Good luck !
0
0
EG
Expert
•
111.4K Messages
3 years ago
BTW, the signal stat ranges / values are in the pinned Troubleshooting Tips topic at the top of this board's page: https://forums.xfinity.com/conversations/your-home-network/internet-troubleshooting-tips/602dae4ac5375f08cde52ea0
Check your signal levels
To view your modem’s status page go to http://192.168.100.1 or http://10.0.0.1
Note: Not all modems will allow you to view the status page and some will have different URLs to access this info. If you are unable to access your modem’s status page, you can contact Comcast Customer Support and ask the support representative for these values.
(edited)
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0
user_f26f9d
Visitor
•
5 Messages
3 years ago
@EG I removed the splitter and connected the cable modem directly to the drop from the pole, and get even more errors in the log. I don't want to waste your time, I'm escalating to Comcast, just wanted to get this additional info out there in case it changes your advice in any way
Downstream power is now out of spec, too high. Upstream power is lower, but still over 50
Status
Profile ID
ID
MER
Number Range
Codewords
Codewords
Codewords
(edited)
0
0
EG
Expert
•
111.4K Messages
3 years ago
Yep. You need a tech out to properly balance the line. Good luck with it ! Please post back with how things turn out.
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