How to diagnose brief losses of internet?

[Benji]

I'd like to preface this by saying I've only just made my first OPNsense setup and that I don't know enough about the systems to know the optimal way to diagnose this issue.

I thought everything went ok, but I've noticed a complete loss of internet, twice, in the last few days. It only lasts 5 - 10 seconds. My ISP has been a little unreliable lately, so it could be them, but I'd like to make sure it's not something I've done.

I had a look through Log Files, but I'm not sure which area I'm supposed to be looking at and what category of log I should be filtering by. I'd be grateful if someone could point me in the right direction.

My setup is:

OPNsense 23.1.9
Optiplex 3020, 8GB RAM, i3-4130 (HT enabled) and a 120GB SSD.
HP NC365T (2 of the 4 ports used)
TP-Link TL-SG108PE
Unifi Flex Mini (connected to the TP-Link)

I have my ISP router in modem mode connected to one of the HP NC365T ports, set as WAN and the TP-Link switch on another of the ports, set as LAN.

I have C3 states disabled in bios and have enabled C2 states in tunables.

Many thanks.

[bartjsmit]

Set up a Smokeping instance and you'll likely see the latency go up before your outages.

It also provides good screenshots to go to your ISP with for refunds

https://www.youtube.com/watch?v=IDl_oVe_WwU

Bart...

[Benji]

Thanks, I'll give that a try.

[Benji]

I have that all setup, thanks. This would obviously be good if it's an ISP issue. How would I diagnose an issue if it's a local problem?

[CJ]

You can use turn on Gateway Monitoring in OPNSense instead of setting up smokeping.  Just go to System->Gateways and uncheck the Disable gateway monitoring checkbox.  That will give you a Quality tab under Reporting->Health.  You should start with monitoring your gateway, not a remote DNS so you can isolate the issue with your ISP.

I would start with that before worrying about your local setup.  Especially if you're on a cable ISP.  OPNSense is unlikely to be the culprit.  If it does turn out that your ISP is stable during the periods where you have connection loss you can describe your network setup more.

[Benji]

Thank you. I've followed your advice and I shall wait and see what comes of it.

[CJ]

Thank you. I've followed your advice and I shall wait and see what comes of it.

Glad I could help.  But can you clarify what type of ISP connection you have?  I'm assuming it's cable because what you're describing sounds like line noise.  That will require you to get your ISP maintenance/infrastructure team involved as the cause is likely due to issues outside of your control/property.