Good News ....

Replace the PoE with a new switch and have one output going to the PoE.

In reply to a post by paving363:

Thanks both. I was watching TV and thinking about all this again so decided to get up and do some testing. I managed to patch a direct route straight through from the router to the office pc with no switches (and annoying the kids in the process!) and hey presto 310mbps in the office! So cabling fine. Then started adding switches back in and there is one that is causing the problem. It’s gigabit POE as has some cctv cameras attached but it is limiting traffic down to 100mbps. So I will get a replacement and should be good to go. Many thanks for the input - learnt a lot.

Well that’s good news and a very fast resolution!

It was a bit puzzling when you said in your OP that you were running consistently at 250/45 at the router. I thought that you actually had two issues to deal with.

Anyhow it’s good you have it sorted. A final word of advice, especially with perhaps many unmanaged switches in your network is that although switches are designed to be cascaded (to a certain degree anyway) you don’t really want to over do it.

Very importantly with all unmanaged switches in the network, try to avoid creating switching loops - where the output of a ‘downstream’ switch goes back to the input of an upstream switch. This can cause all sorts of weirdness, unless the switches are managed or have the capability of having spanning tree protocol enabled on the network which breaks topology loops but keeps redundant links.

If you’re unfamiliar with the concept of switching loops, see this video:
https://youtu.be/liRdZ5p1Xp4

The guy does a pretty good job of explaining spanning tree here too:
https://youtu.be/y5JiPUYUjBg

As you can probably guess from the OP, the network has 'evolved' over time. Cameras being added has generally necessitated POE switches to be put in at various points but then also adding feeds to the outbuildings. I'm lucky in the sense that we have a walk-in attic space, which accomodates a lot of the cabling. It's a bit of a birds nest now but I do know what is what - I pity anyone else trying to work it out though! I did at one point have a switching loop which was killing the feed on some cameras - took me a while to work that one out but now have everything running out from the router/patch panel as you describe and it is working well. One other thought that might be usefule related to the FTTP install. We were limited to where the fibre could come to on the house from the pole outside, meaning the ONT wasn't in the ideal place and certainly not where I wanted the router. The Openreach engineer was rather surprised that I was able to add a new ethernet connection from next to the ONT to and terminate it in the 'comms' cupboard in the middle of the house (but can get cables through to from the attic luckily) - that allowed me to locate the router there and it works absolutely no problem. I have also upgraded the wifi (we have a couple of APs in the house) to gigabit dual band and that has made a big difference too. So hopefully is now working well. Until of course I try to add the next thing! Thanks again for all of your help - very satisfying to be reolve this sort of problem.

You don't need PoE switches though. You can use PoE injectors and often much more cost effective

The switches appeal beacsue you can run multiple cameras from one power sourse. Can you get multiple device injectors as otherwise you end up needing a load of power sockets available?

Plenty of multiway PoE injectors around - just need to find the right spec. Or if they have individual injectors you can get power leads with one 13A plug and several trailing "cloverleaf" ends.

Thanks for that - will take a look.

I probably prefer the opposite to MHC (when it comes to PoE at least) 😀

Tend to have a lot of gear which is increasingly PoE powered...DECT and WiFi access points, Cisco IP phones in our office, HIKvison compact PTZ cameras, smart bridges for Philips Hue lighting, SimonsVoss door entry, SensorPush gateway for temp/humidity sensors.

There's other stuff which is just more convenient to power over the data cabling, even if the devices are not native PoE - so use TPLink 'splitters' with a 5/9/12VDC selectable output voltage for that - the data network becomes a distributed power socket!

Probably just over three-quarters of the stuff with a wired connection actually needs PoE. So preference is definitely one box and the plug and play - plug in a device in whether it’s PoE (or not) and know it’s “fed and watered” for both data and power. Keeps my comms cupboard tidier too.

Other approaches equally valid - just comes down to approach/preference and circumstances 😎😂

In reply to a post by paving363:

Thanks both. I was watching TV and thinking about all this again so decided to get up and do some testing. I managed to patch a direct route straight through from the router to the office pc with no switches (and annoying the kids in the process!) and hey presto 310mbps in the office! So cabling fine. Then started adding switches back in and there is one that is causing the problem. It’s gigabit POE as has some cctv cameras attached but it is limiting traffic down to 100mbps. So I will get a replacement and should be good to go. Many thanks for the input - learnt a lot.

out of interest what model of switch was it?

Thanks
Dan