I have a C-7, running 2.3.9.201, and it's prone to losing LAN access; this was first raised towards the start of this year (admittedly in a request for help getting diagnostics, rather than solving the problem itself), and TBH a solution has never been found.
In summary:
When the problem occurs the hub stops responding to or sending anything on the LAN. Blocked activities include:
Main UI page, and the Diagnostic Tool (the pages for both time out if you try to view them)
Scheduled Cloud backups
LAN-based devices (Kasa/Tapo)
Remote Admin, Cloud (and Local) Dashboard
Alexa control, OwnTracks updates
The hub has a DHCP reservation on the router.
When LAN access is down ZWave and Zigbee device triggers and control continue to work, as do all non-LAN-related rules,
When LAN access is down the hub LED is green.
I've tried changing network cables and power supplies; there's a switch between the hub and router.
AFAICS there are no Jumbo frames on the LAN.
I've restored the DB from backup a few times.
No obvious pattern or trigger for the problem; several weeks can go between occurrences, but it can also happen more than once in a single day.
If anyone can suggest anything to try I'd welcome the input!
What kind of switch? Gigabit ethernet? Or Fast ethernet? Can you try an older fast ethernet switch if you are not currently using one? And if you are using one, then it definitely eliminates JF as a culprit.
Gigabit (a PoE one, FWIW, although not powering the hub itself). Thanks for the suggestion, but unfortunately I don't think I have a fast switch at all these days...will have a rummage in the old parts cupboard later, but not very hopeful.
It's more a stopgap than a solution, but I might put a periodically run rule in to ping my NAS, and reboot the hub if it can't get a response...
So you have a switch separate from the hub... Can you plug the hub directly into the router instead of the poe switch? Just to eliminate that as a possibility? Also do you have Jumbo Frames turned on anywhere?
I think I've got a spare cable somewhere that'll be long enough - will give that a go, ta. I've checked everything, and AFAICS there isn't anything using Jumbo Frames on the LAN.
An update on this; I did have a suitable cable and have swapped it in (around 10 days ago), and... ...none of the LAN problems since then. Provisional s,
Given the intermittent nature of the problem it's impossible to be sure it's actually stopped at this point, but so far, so good.
So, thanks again for the suggestion; detailed network ins and outs aren't my strong suit, so just wondering if there was a specific thing switching to the router was intended to address?
Or the router's [vague hand waving] filtering out some sort of traffic the switch is letting the hub see, and that traffic's causing the problems?
As above, my knowledge of LAN behaviour's pretty limited so no idea what that "traffic" might be, or whether I'm way off base and the basic idea's a non-starter.
Switches don't output anything, they simply pass the traffic they are given. (now on enterprise managed switches this can be different but unless you're running something like a catalyst switch with weird stuff turned on for vlan and trunking and NAC it's not something you will have to worry about). So the switch isn't passing traffic properly. If you swap the switch out I'm sure that everything will work normally. Your router also won't be rejecting anything if it's a typical consumer unit. Unless you have to build rules that do packet inspection it's not something that will happen either. (Why yes, I am a network engineer, lol) Swapping out a consumer switch is pretty cheap.
Everything on the LAN is consumer-grade, and there's no VLAN in the setup - the only hub-specific setting on the router is an IP address reservation, so AFAICS there's nothing fancy that might be muddying the waters.
That switch does need to provide PoE (it powers a doorbell cam) but as it turns out I have a spare PoE switch I'm planning on using elsewhere in the house in the near future. So I'll try swapping that in, switching the hub to it (that switch has an unpowered socket, so I'll use it just in case that's somehow a factor) and sit back and see what happens.
Update to follow, once there's either been a hang or it's been long enough to call it as "still good".
Just to throw a wrench in here, did you try changing the cable between the switch and hub, or just use that new cable you plugged directly in the router and plug it in the switch. I've had similar problems in the past on a PC and it finally came down to the wiring in the wall that had gotten chewed on by a mouse. Just an idea to further diagnose your problem and make sure it's actually the switch.
All wrenches welcome, and to answer the question that hasn't been tried (yet).
I am all for trying to find the easiest solution, though, so before any wholesale replacement of the switch I'll try swapping the current router-switch cable with the "proven good" router-hub one, and put a new short cable between switch and hub. That'll involve significantly less balancing on a sofa arm to get at the top of the bookcase where the switch and hub live, which has to be a good thing.
It's more a stopgap than a solution, but I might put a periodically run rule in to 
...none of the LAN problems since then. Provisional 
s,
