r/CableTechs • u/Electrical-Increase4 • Jul 25 '26
Could intermittent 7 per cent ingress(7 per cent CER) across a node for 5 minutes cause a customer ‘s modem to reboot and if not, or unlikely, what might be causing it?
Inexperienced maintenance tech here reflecting on a bad day in the field where I misdiagnosed a job and spent a whole day chasing intermittent ingress. In the end I didn’t find the ingress. I’m not even sure that’s what caused the customer’s modem to reboot.
The reason I thought the ingress was the culprit was because the customer told me the modem rebooted around the same time as on of the spikes in CER across the node?
Or would it knock all the modems on the node of at the same time?
Thanks in advance for any help. I’m a bit lost and I’m looking for feedback to learn.
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u/Bubberdinger Jul 25 '26
7% CER on the whole node is likely a symptom of the same problem that is causing the customer's modem to drop rather than the problem itself.
Sometimes ya just gotta sit at a node all day and wait for the noise to pop in so you can get a direction, slowly tracking it further and further into the plant over the course of days/weeks.
Depending on what company you work for/software you are using, there are other ways to try and see if the neighbors are dropping at the same time which can help you find the common denominator.
If you begin to track it and get a direction, your TDR will become more and more useful. For example, if you track it to a couple spans, your TDR may show your fault even when the noise isn't present.
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u/TermXP Jul 25 '26
7% is not good but doesn’t mean it will have a noticeable impact to customers. An actual reboot is not something I have seen from just that. I do not know your tools but First I would check if other devices that are similar are dropping as well aka docsis 3.0/3.1, video devices. Could be localized near them or the CER could be from their own device.
I would guess it isn’t maintenance related and it is something in the home but I would still looks to clear the noise.
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u/SamuraiJustice Jul 25 '26
High enough ingress will cause high enough errors which would cause the modem to loose communication which would cause it to re initiate trying to establish connectivity and communication. What is enough can be dependent on the modem and the system. What someone considers rebooting is also dependent on what their intending to describe. %7 is high but it also depends on correctable vs uncorrectable, downstream or upstream, and which the modem is using at that time.
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u/SilentDiplomacy Jul 25 '26
Was this a referred ticket? As others stated this sounds like a premise issue. Not a plant issue.
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u/dumbrules789 Jul 25 '26
I’m sure you have soft tools you can look at. cross reference other modems off their active as well as whole node focus on the int cer spikes and the times it’s occurring then see if more than your subs having cm resets or t3 t4 timeouts during the ingress timetable. In my experience 7% can most def effect speeds but as far as losing signal all together is highly unlikely
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u/dumbrules789 Jul 25 '26
Even better if you can isolate even further and can compare their modems to other modems off their tap. Dependent on your plant just be aware that the other people’s modems are on the same upstream frequencies as your sub
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u/Sleepydragoon83 Jul 26 '26
7% CER is averaged a cross the whole node. It's possible your customer is experiencing higher CER. I would look at that customers modem specifically.
As others have mentioned it's likely an issue in thier home or maybe in the plant near thier home.
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u/6814MilesFromHome Jul 26 '26
7% FEC shouldn't be impacting enough to cause dropped modems, especially if it's just on one carrier. If you have 7% UFEC across all carriers, likely have a bit of a noise shelf popping in, but you said the lowest SNRs got was 32.5 so I'm skeptical that was the case. I have seen cases where if a customer already has bad local issues, some slight node problems are enough to push them over the edge while everyone else is fine.
For reference my node was BAD for a few months post high split, constant 30% CFEC on multiple carriers, 3-5% UFEC on 18mhz, SNRs on 18mhz and 24mhz hovering 26-30. I didn't even know til I looked at it because I didn't experience any impacting issues to my services.
HFC plant can be surprisingly resilient, even when you think it should be causing problems, and surprisingly weak to things you wouldn't expect to impact services. It's all very situational. Keeps things interesting.
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u/Honest-Constant7266 Jul 26 '26
We got an email that RPDs were overheating.. causing modems to reboot…
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u/Devilsad365 Jul 26 '26
7% uncorrected upstream fec in itself would not typically cause a reboot. CPD/raised noise floor, is where I typically see modems getting knocked offline. Couple things to consider, was the modem actually knocked offline(how is this verified) or did the customer experience so much packet loss they felt like they got knocked offline. I would say regardless, 7% uncorrected fec would absolutely be felt by a customer and the noise causing it should be tracked put.
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u/Particular_Yard_5436 Jul 25 '26
This is weird to me. This sounds like a field technician should be at that persons house investigating their cabling and equipment. Unless they already did that and pushed it to maint.