Upload speed dropping to single digits. Dowload drops to 25 to 50% (original) (raw)

February 7, 2025, 4:26pm 1

What diagnostic tools can help me better analyze this issue?

We are using Spectrum Business on a coax-based connection, provisioned for 600 Mbps down / 35 Mbps up. A Spectrum technician identified a line issue—possibly in the coax leading to our building or out to the road. They mentioned encountering errors but didn’t provide further specifics.

The primary symptom is that speeds degrade to the low single digits over time. The only temporary fix is power cycling the Spectrum modem and router, which restores performance for a while, but the issue inevitably returns.

We’ve ruled out our own hardware as the source of the problem. What tools or monitoring solutions can help us better diagnose the root cause and present clearer data to Spectrum for resolution?
The wiring- coax and ethernet cables - and equipment is all only three months old.

jessevas (jessevas) February 7, 2025, 6:39pm 2

How did you rule out your own hardware? I had a similar issue with a router/firewall. We diagnosed it as our hardware by taking it’s temperature because all the other tests we could run came back clean.

jadrien (Jim Peters) February 7, 2025, 6:52pm 3

Direct ethernet cable plugged into Spectrum router of their modem,-router pair.

jessevas (jessevas) February 7, 2025, 6:56pm 4

Is that your layer 1 demarc? Or are you also responsible for the input cable from the outside block to the modem? If you’re responsible for the cable, I’d inspect and test all connection points between starting with the ones outside.

I’d also take a temp reading on their gear, just to see if it’s the problem.

benoitt (BenoitT) February 7, 2025, 7:10pm 5

I hate those issues; they’re really difficult to deal with.

In short, there’s nothing you can do, except call Spectrum when the speeds drop. They’re the only ones that are capable of pulling data from the cable modem, so they can tell that there’s an issue. They’re not shy about giving you tons of warnings about charging you to send a tech out to you either.

So… call them, and log your calls. If you have an account rep, reach out to them. If you’re lucky, you’ll come across a friendly tech, who knows exactly what’s going on in your neighborhood (some of these techs are Pure Gold).

We had this happen recently in my area, but it turns out they were doing DOCSIS 3.1 upgrades. It still took 6+ weeks to resolve.

jessevas (jessevas) February 7, 2025, 8:37pm 6

True. My last employer had Comcast out several times for an issue that they swore wasn’t there until it happened while they had both a tech at our shop and a tech at the nearby hub (by coincidence). Only then did they acknowledge that it was on their side.

b-c (B-C) February 8, 2025, 6:33pm 7

Tap issue…

Provider modem usually 192.168.100.1 will resolve their diagnostics page…
Throw the upstream numbers and possibly downstream numbers into one of the AI Bots to analyze …

Usually this is an issue Where the Coax meets the trunk… Common issue…
Fighting a similar one myself… Tier 1 techs might catch it but rarely do…

This is a recent output I was checking over the last month…
This why if possible I always get my own Cable Modem… so I can easily see these values…

1. Flux (Fluctuations) at the Tap

2. OFDMA Fail at the Tap

adrian_ych (adrian_ych) February 9, 2025, 12:31pm 8

From OPs post…ISP tech came and “identified a line issue—possibly in the coax leading to our building or out to the road”…

adrian_ych (adrian_ych) February 9, 2025, 12:33pm 9

Get another ISP ?
Use ur SLA to nego end of contract & compensation

matt7863 (m@ttshaw) February 9, 2025, 4:19pm 10

Then Spectrum need to come and test and replace that. their service to you is either to the customer output of the modem or possibly even the customer output of the router.

Do you definatley need to power cycle both?
If just router - it is a router issue - not uncommon, memory link, hardware issue etc usually present over prolonged uptime.
If just modem - replace modem.

A true cable issue would not be fixed by a reboot of any device - there either is or is not a signal issue.

jessevas (jessevas) February 10, 2025, 1:42pm 11

I get what you’re saying. But he also goes on to say that he ruled out his equipment, understanding that what the tech is saying "…issue - possibly in the…: isn’t necessarily answering any questions about their own equipment. It is possible to have more than one problem in the same system, and to have one problem masquerading as another.

L5257 (L5257) February 10, 2025, 1:53pm 12

Make sure that the MTU on your WAN interface is set appropriately. You could be running into excessive packet fragmentation on the egress interface.

Also check to make sure that you have a statically set duplex setting on the WAN interface. Whatever the maximum speed is for the upstream device. Auto-negotiation is a common issue with some CPE.

adrian_ych (adrian_ych) February 10, 2025, 4:11pm 13

Actually if you are or had worked for ISP and/or data centers etc, you may find that this type of issue is rather quite common…

In the distant past, 10/10 (10mbps up 10 mbps down) or 50/20 or 50/50 etc type of packages were often marketed … then some ISP just went 100/100 or 200/200 where the numbers are easier to manage that 600/50 or 600/35 which literally is meaningless in our gigabit network world of 2020 or 2021 ??

So what it means is that the ISP might have like 20x 1Gbps & 5x 10Gbps at the distribution box into a building then need to “tap” a 600/35 connection to one of their customer which always get issue (flooding or something) where once the connection restarts, no issue then it gets flooded somehow.

jadrien (Jim Peters) February 11, 2025, 5:09pm 14

Spectrum is still working the issue. Friday it was horrible all day. Yesterday and today it looks like it may be solved. Their devices - the cable modem and router are more minimalist with blinking lights that prior versions. One blue/red/off on the router, two on the cable modem that are blue or white.

The Web Interface offers nothing more than a green dots and no line information.
What is in the system log on it is not meaningful to me.

adrian_ych (adrian_ych) February 12, 2025, 4:32am 15

I would recommend you talking to other ISPs and/or considering a more conventional business broadband that uses like 100/100 or 500/100 (UL/DL speeds) ?