Baffled over strange behaviour

[TheForumTroll]

I'm having a strange problem and I have no idea where to even start. I'll try my best to explain:

At seemingly random intervals (we are talking days or weeks), the network suddenly goes down for the PCs on our LAN. Between these PCs and OPNsense there is 1 Cisco and 1 HP (fibre) switch and the connection to both of those also dies (from the PCs LAN). No WebGUI, no ping. Each time it has happened I've run around like a headless chicken trying to fix it by rebooting the switches, rebooting PCs, etc. etc. because surely it must be here the issue lies. Well, the fix was to reboot OPNsense - then everything comes up back again. But how does OPNsense taking a crap kill ping to a switch two hops away?

A simple diagram:

Several PCs connect to Cisco switch ----> HP switch connecting different LANs ----> OPNsense ---- Internet ---> Dragons

I tried using Wireshark, but couldn't see anything out of the ordinary, but then again I'm no expert. The fix for now is using an older OPNsense box, but it is a bit too slow to handle the almost 1 Gbit/s traffic, so I got to get the newer one running as soon as possible.

Running latest version (23.7 I believe?) on both boxes.

[CJ]

What WebGUI are you attempting to connect to?  OPNSense or something else?

What are you pinging?  You mention being unable to ping a switch?

What does the network going down for the PCs look like?

[TheForumTroll]

OPNsense WebGUI. I can't ping anything at all (except my own IP and localhost). Not even the switch the PC is connected directly to, two hops away from OPNsense. I've checked that the IP on the machine is correct of course. As soon as OPNsense dies every other device (at least the ones with a screen and keyboard I can test from) also dies. Reboot OPNsense and everything is back.


Edit:

I forgot to add that with OPNsense powered down the network works just fine (except through OPNsense of course). It is only after the box goes down by itself that everything else goes with it.

[CJ]

Can you draw out a network diagram?  Can you ping any other pcs?

You mention different LANs, do you mean VLANs?