This topic

LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 16:21:39 GMT

Hello,

I am trying to solve a particularly troublesome network issue.

My office is remote from the main house, and that is where the main BT connection comes in. Before Fibre, I connected the BT Hub to the rest of the house using a LAN, and the rest of the house had a router which ran the House WiFi. Worked perfectly for 12 years. At the office end, I used an ethernet switch to connect to the LAN, and had comparable speeds in the main house to what I was seeing in the office. I changed the router in the house a few times as it got old, but otherwise its been a very good system.

Now - we had fibre switched on a few weeks ago - I am using the same smart hub I always was, but I cannot get a signal through the LAN to the rest of the house. I know the LAN port on the smarthub is delivering the promised 900 Mbps, as I checked it with a lap top, but connect it to the LAN and it disappears somewhere, never to be heard from again!

I have changed the ethernet switch for another (Does this need to be able to cope with fibre speeds; it is quite old?). I have swapped the router at the house end for another but as I am not getting a signal in the house anyway, that isnt going to help. I have checked out the wiring, and ensured there is continuity between the office and the house (there is).

I have been using a Mesh WiFi to get internet into the House, but the speeds are shocking. The 900 Mbps is throttled to about 290 just by connecting the first node, and by the time it reaches the main house, speeds are down to between 5 and 12 - so thats a waste of time. If the connection between the office and the house was working, I think this would be a good solution, but I cannot for the life of me work out why I cannot get a connection!

I did try a Powerline adaptor, thinking I might be able to get it to work through the power circuits - it flickered into life briefly, but has since failed, so thats going back to Amazon!

I'd be grateful for any ideas! I am missing something, but this isnt my area of expertise!!

Thanks in advance

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 16:54:12 GMT

So, if I’ve read that right, the office is ONT to SH2 to switch then to rest of house? The rest of the house is not getting anything at all.

What about the other switch ports? Do they work if you plug a device directly into one of them? If not, I would try a factory reset on the SH2. (Just be aware that will clear any custom settings, so back them up first).

It could also be a switching loop, where you have a loop connecting back to the switch, but modern switches tend to have (R)STP that should correct that.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 17:00:18 GMT

Thanks for this - really appreciate your reply.

I have tried two SH2's, and they are the same - I can connect to the LAN ports on the SH2, and get 900 Mbps on a laptop, but connect anything else and nothing is happening. The ethernet switch shows its happy flashing light where it is plugged in to the SH2, but the outgoing ports show nothing, so I wonder if that could be part of the problem. However, if I just connect the SH2 to the LAN directly, I still dont seem to get a signal at the other end in the house (so bypassing the switch). However, I am clutching at straws here!

It is very odd - it did work, and now it doesnt, and nothing changed, except fibre was switched on!

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 17:07:12 GMT

It sounds as though it has to be a fault with the cable to the house, but you said you'd check that?

Did you check it with a proper cable tester? It's possibly just one of the plug pins failing to connect.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 17:26:16 GMT

Thanks again for your reply.

yes I bought a continuity tester from Amazon and also swapped over the socket at the office end with an unused one. The house has four connections from the office; none of which seem to be working. One of them was known to be faulty prior to the fibre installation but the others worked. All very strange!

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 17:30:17 GMT

But they test as OK? Weird. Sorry, I'm out of ideas. (I bet it will be something blindingly obvious. It usually is).

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 17:44:56 GMT

I’m glad it isn’t just me! I will go back to basics tomorrow and have another go. I’ve also ordered another Ethernet switch in case that might be it. The kids can’t play Fortnite right now so you can imagine how much trouble I’m in!

many thanks for your support.

bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 17:51:28 GMT

I thought you said you'd already tried a different switch?

If not, I 'd try a factory rest on that switch before you order a new one.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 17:54:45 GMT

Ok, thanks. Yes I did, but it is a good few years old. I will have another go tomorrow!

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 18:07:22 GMT

I take it the power light is lit?

Could be memory failure.

Silly question. I take it the ONT is connected directly to the WAN port on the SH2 and it is set for FTTP mode? If you are trying to connect the ONT through the switch as well as the LAN you'll have problems.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 18:19:30 GMT

Thank you.

yes the ont is connected to the SH2 and then that is connected to the switch. However, talk to me about FTTP mode. How can I check that please?

bruce

Re: LAN issues following fibre installation

gg30340 — Thu, 13 Aug 2026 18:21:39 GMT

It may be me but I am confused about your set up. Can you clarify your set up and if possible upload a diagram of the set up:-

How far from the house is your office?

Is the Fibre ONT is in your office or the house?

Is the Smarthub in your office or the house?

You have run an Ethernet cable from the your house to the office?

Is the ONT connected directly to the Smarthub?

What is the Ethernet cable to the office connected to at either end?

Is the Ethernet sited in the house or office and is the Ethernet cable connected to a port on the Smarthub and what device connects to it in the office.

You say that you are using a Mesh to "get Internet into the house" this implies that your Smarthub is in the office or are you running two routers, one being in the house and one in the office?

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 18:32:14 GMT

@gg30340 Ah, two routers. Good point.

FTTP mode is a setting in the Smart Hub 2. Makes LAN port 4 act as a WAN port. The ONT has to connect to a WAN port. I can't remember exactly where it is, as I don't use an SH2 these days, but if you look through the management pages on the SH2, it's not difficult to find.

Re: LAN issues following fibre installation

licquorice — Thu, 13 Aug 2026 18:33:01 GMT

The only changes necessary was to disconnect the hub DSL port from the master socket, set the SH2 to fttp mode and connect the ONT to port 4 on the SH2 with an ethernet cable.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 18:36:48 GMT

Thank you. Pretty sure all that was done. It works perfectly in the office; just not anywhere else!

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 19:15:45 GMT

Just to expand on gg30340's point, you can't have two routers in the network.

If you connect two, only one of them can be functioning as a router, in this case the one in the office. The one in the house has to be connected LAN port to LAN port, (with FTTP mode off, if it is another SH2). If you get a mesh system, the mesh unit must be in access point mode, not router mode.

Re: LAN issues following fibre installation

brucewgordon — Thu, 13 Aug 2026 19:29:11 GMT

Thanks for replying.

office is part of the house, but sits above the garage, which is at 90 degrees to the main house.

fibre ont is in the office. Fibre works perfectly up there.

smarthub is in the office

yes there is Ethernet cable between house and office. I had it installed when the house was built and it has worked perfectly to now.

there is a wall mounted Ethernet port in the office, which is connected via a 4 port switch to the SH2

At the moment there is one router, the SH2, but I have been running a second as a WAP for years.

Bruce

Re: LAN issues following fibre installation

WSH — Thu, 13 Aug 2026 19:40:00 GMT

Yes, weird. Even if that ethernet cable was old cat 5, you should still see 100Mb/s. Anything 5e or above should be fine.

Re: LAN issues following fibre installation

gg30340 — Thu, 13 Aug 2026 22:36:31 GMT

You may already have done this but if not I would carry out a process of elimination using your laptop. Make sure you turn its wireless card off to ensure it is only using the Ethernet connection.

The ONT and the hub appear to be working OK so disconnect anything that is connected to the hub other than the WAN connection.

Disconnect the Ethernet switch. Why is it there, do you need it over and above the Ethernet ports on the hub?

Connect a known good Ethernet cable from the hub directly to the wall mounted Ethernet port. Connect your laptop to the other end in the house where the wall mounted Ethernet cable terminates and using the laptop ensure that the Internet is working.

If the Internet is not working the fault lies either with the wall mounted Ethernet port or the Ethernet cable to the house or the termination socket in the house.

If it is OK then you could reconnect your four port Ethernet switch if it is required and test each of its ports using the laptop although I would leave it disconnected until you have established where the fault lies.

If it is good move onto the house.

You never mentioned how your WAP/ Mesh is connected to the hub i.e is it by Ethernet or Wi-Fi and if it is producing a wireless signal. Presumably the password to access the WAP/Mesh has been checked and is correct and if you are using the same hub it will be the same as that although I would suggest that you use a different one from the that of the hub so that you know you are connecting to the WAP/Mesh and not the hub.

Re: LAN issues following fibre installation

brucewgordon — Fri, 14 Aug 2026 11:26:42 GMT

Many thanks for this - I appreciate your time.

There appears to be no signal between the office and the house, which does indeed imply a wiring fault. However, I have done a continuity check with a CAT5 tester, and that shows it as being ok. Coupled with that, it worked just before the switch over, and then failed immediately after!

I will go back to basics and try again - it is a very frustrating problem!

All the best

Bruce