on 11-02-2023 02:25
Hi all,
TL;DR - Shibboleet help please! Am I being a muppet or is this upstream?
For background - I'm a Linux analyst and CCNA qualified but know very little about DOCSIS.
I'm getting occasional T3 (and previous T4) dropouts plus a bunch of Post-RS errors. I understand this is bad! 🤔
VM Superhub 3.0
Hardware version : 11
Software version : 9.1.2109.200
Last reboot: 06/02/2023 ~18:40
My first concern is that the superhub was delivered without a coax cable so currently have no primary isolator (I have the PSU into the VM wall-box setup... I'd love to know how this works!)
I'm currently using about 5m of CT100 cable, kept from last year's VM subscription.
Secondly, I noted a kernel panic in the logs when I first booted it! This has since disappeared.
Here's the log. 23:43 was when my Twitch broadcast dropped for a few seconds:
Time Priority Description
11/02/2023 01:25:37 | notice | LAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
10/02/2023 23:43:22 | Warning! | Lost MDD Timeout;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
10/02/2023 23:43:17 | critical | SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
10/02/2023 23:43:16 | Warning! | RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
10/02/2023 23:43:16 | critical | SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
10/02/2023 13:11:38 | critical | No Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
09/02/2023 15:49:5 | Error | DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
06/02/2023 18:43:51 | notice | LAN login Success;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; |
Up/Down metrics in comments due to character limit.
TIA. Rich.
on 11-02-2023 02:26
Here's the Metrics:
Downstream:
Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID
1 | 426250000 | 5 | 34 | 256 qam | 9 |
2 | 362250000 | 4 | 34 | 256 qam | 1 |
3 | 370250000 | 4.4 | 34 | 256 qam | 2 |
4 | 378250000 | 4.5 | 34 | 256 qam | 3 |
5 | 386250000 | 4.5 | 34 | 256 qam | 4 |
6 | 394250000 | 4.9 | 34 | 256 qam | 5 |
7 | 402250000 | 5 | 34 | 256 qam | 6 |
8 | 410250000 | 5 | 34 | 256 qam | 7 |
9 | 418250000 | 5 | 34 | 256 qam | 8 |
10 | 434250000 | 5 | 34 | 256 qam | 10 |
11 | 442250000 | 5.3 | 34 | 256 qam | 11 |
12 | 450250000 | 5.1 | 34 | 256 qam | 12 |
13 | 458250000 | 4.9 | 34 | 256 qam | 13 |
14 | 466250000 | 5 | 34 | 256 qam | 14 |
15 | 474250000 | 4.8 | 34 | 256 qam | 15 |
16 | 482250000 | 4.6 | 34 | 256 qam | 16 |
17 | 490250000 | 4.5 | 34 | 256 qam | 17 |
18 | 498250000 | 4.4 | 34 | 256 qam | 18 |
19 | 506250000 | 4.3 | 34 | 256 qam | 19 |
20 | 514250000 | 4.1 | 34 | 256 qam | 20 |
21 | 522250000 | 4 | 34 | 256 qam | 21 |
22 | 530250000 | 3.9 | 34 | 256 qam | 22 |
23 | 538250000 | 4 | 34 | 256 qam | 23 |
24 | 546250000 | 3.9 | 34 | 256 qam | 24 |
Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors
1 | Locked | 34.4 | 154939 | 6519 |
2 | Locked | 34.4 | 182167 | 6062 |
3 | Locked | 34.3 | 346294 | 6061 |
4 | Locked | 34.3 | 280815 | 5980 |
5 | Locked | 34.4 | 284593 | 6431 |
6 | Locked | 34.9 | 179684 | 6656 |
7 | Locked | 34.4 | 166645 | 6647 |
8 | Locked | 34.4 | 263489 | 6408 |
9 | Locked | 34.4 | 158990 | 6862 |
10 | Locked | 34.9 | 107150 | 6441 |
11 | Locked | 34.9 | 98195 | 6398 |
12 | Locked | 34.4 | 201984 | 6314 |
13 | Locked | 34.3 | 193419 | 6179 |
14 | Locked | 34.4 | 135915 | 6478 |
15 | Locked | 34.9 | 150725 | 6554 |
16 | Locked | 34.9 | 155710 | 6611 |
17 | Locked | 34.4 | 246839 | 6512 |
18 | Locked | 34.3 | 141611 | 6566 |
19 | Locked | 34.3 | 185919 | 6557 |
20 | Locked | 34.4 | 226785 | 6648 |
21 | Locked | 34.4 | 341202 | 6559 |
22 | Locked | 34.3 | 290900 | 6489 |
23 | Locked | 34.4 | 189801 | 6580 |
24 | Locked | 34.4 | 116016 | 6531 |
Upstream:
Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
1 | 46200000 | 36 | 5120 | 64 qam | 3 |
2 | 39399965 | 36 | 5120 | 64 qam | 4 |
3 | 60299951 | 35.8 | 5120 | 64 qam | 1 |
4 | 53699971 | 36 | 5120 | 64 qam | 2 |
Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts
1 | ATDMA | 0 | 0 | 0 | 0 |
2 | ATDMA | 0 | 0 | 0 | 0 |
3 | ATDMA | 0 | 0 | 1 | 0 |
4 | ATDMA | 0 | 0 | 0 | 0 |
on 11-02-2023 07:21
Possibly the cable you're using is not adequate for cable internet, which is hugely vulnerable to radio interference if the wrong cables are used. VM normally use their own triple shielded RG6 for that reason. I'd suggest you're looking at booking a £25 non-fault call out to have the connection looked at, the hub connected with the right cable, and SNR checked.
on 11-02-2023 12:18
Thanks for the info.
Do you have the specs for this cable?
Standard RG6 is single aluminium shielded. That's why I've always used CT100. Same impedance, same attenuation but duofoil shielded and harder to kink.
on 11-02-2023 14:46
Quick update.
I've put it on a 0.5m cable cut from a fresh reel and I'll contact support on Monday to get a VM supplied one.
11-02-2023 14:59 - edited 11-02-2023 15:13
If the PSU into the VM wall box is like this, it is an RFoG / FTTP area.
The PSU via the coax is powering an ONU in the external OMNI box.
on 11-02-2023 15:21
Nice one. Thank you @Client62.
That's my exact setup.
I guessed it was FTTP
I assume the external piece of kit is effectively an ER fibre to RF modem.
Seems kinda mad that it isn't simply converted to copper ethernet.
Thanks for the details. I'm going to have some fun on Google this afternoon 😁
11-02-2023 15:27 - edited 11-02-2023 15:30
I agree with the comments about coax cable quality being suspect for the following reasons ...
We are an RFoG area with a 10dB attenuator on the Hub3's coax - our Downstream Power levels are about 8 dB below those shown above.
But our Hub3's Downstream SNR figures are higher (read better) , and the number of Pre RS & Post RS errors are minimal.
If the Post RS (Reed-Solomon) i.e. the uncorrectable errors can be sorted a smoother connection should be possible.
PS ... for primary isolation, the 50+ meters of fibre cable will see to that.
on 11-02-2023 15:35
on 11-02-2023 18:32
I think you may both be bang on about the cable.
4h after swapping to a short cable - Zero Post RS errors and zero warnings.
I'll keep an eye on it for a couple of days and do some reading so that I can understand the power and SNR thresholds.
To be fair, I should have just run a longer ethernet cable in the first place, I was just being lazy 😁
Thank you very much for the docs and technical info.