Symptoms
- Internet is unstable or slow and you want to check the modem's own diagnostics
- ISP support asked for specific signal numbers from the modem
- Modem's status page shows numbers you don't know how to interpret
- Trying to determine if a problem is your equipment or the provider's line
Likely causes
- CommonWanting to self-diagnose before or during a call with the ISPSignal statistics can confirm whether a line issue exists even before a technician visit.
What to do
- Log into the modem's admin page (often at 192.168.100.1 for cable modems) and find the status or signal page, sometimes labeled 'DOCSIS' or 'connection status'.
- Check downstream power level, which is generally healthy between roughly -7 and +7 dBmV; consistently outside this range suggests a line issue.
- Check upstream power level, generally healthy between about 35 and 49 dBmV depending on the modem and provider; values at the high end can indicate the modem is straining to reach the provider.
- Check the signal-to-noise ratio (SNR), where higher is better; values below about 30 dB on downstream channels suggest a noisy line that can cause instability.
- Note if any specific channels show 'uncorrectable' or high error counts, which points to a specific frequency or line problem rather than a general issue.
- Take a screenshot or write down these specific numbers before contacting your ISP, since sharing exact values speeds up their diagnosis significantly.
- Understand that a single reading can be a momentary snapshot; if possible, check again at a different time to see if values are consistently poor or only occasionally so.
Tools and parts
- Access to modem's admin page
When to call a pro
If signal levels are consistently outside healthy ranges, share the specific numbers with your ISP, since this typically confirms a line issue needing a technician visit rather than a router or Wi-Fi problem.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.