Full Fibre -Speeds all over the place

Had BT full fibre installed approx 4 weeks ago, I am on the 300mbps package

First two weeks it was lovely 300mbps, 37 MB downloads, since then very different picture, upload has remained consistent throughout but download keeps reverting to anywhere from 65mbps to 89mbps, on the odd occasion it will then go back to 301 mbps.

Had Open reach out twice, got a third visit tomorrow, so far ONT replaced and the SMARTHUB 2, surely the problem is the external cabling, profile or at the exchange itself
Any ideas from here before I get the run around again tomorrow from openreach

Provide information on your testing setup please.
1. Is this tested using a wireless or wired connection?
2. Have you tested with a machine directly connected to the ONT - no router or SH involved in the connection. Note you will need to setup a PPPoE client directly on the machine attached to the ONT to make this work.
3. What is the spec. and approx. age of PC and what operating system are you using to test with.
4. Are you running any AV or spam protection software?
5. Finally do you have you access to another machine(s) to test with?

1) Wired direct connection to router with everything else removed
2) Not yet - Will try this if still the same by end of week
3) AMD 2700X 32MB RAM 3080 RTX WINDOWS 10
4) Only the standard windows defender stuff
5) Tried on a [censored] laptop, 100% same results


I can sit here and spam F5 on a speedtest site and get 85 on average 19 times out of 20, then on the 20th might say 301, rinse and repeat

Edited by deleted (Tue 15-Jun-21 12:16:43)

On top of Pheasant’s good advice …

If a profile was the issue as you suggest, then throughput speeds would consistently hit that profile, not wander about.

If the external cabling was borked it would either work, or wouldn’t work.

The issue is most likely either your kit, as Pheasant covers, or congestion from the head end going back.

Make a direct connection to the ONT, and use fast.com for speed tests, this is the speed test they like to see results from

This all started when my neighbour was connected as well (We are on pole not ducts), I can't see how its my kit, for example when connected to my wider network to my switch the xbox will work at 37.5 MB download when all is good, when its back to 85mbps then it reduces significantly.

For it to be my kit it would need to be the router (replaced), ONT (replaced), laptop (Yeah its [censored] but capable of 300mbps), my pc (Any excuse to upgrade would be good ) , XBOX Series X



In short, got to be outside the premises

They (BT) have done checks their end and are seeing the 85 ish speeds as well, hence why a third engineer visit

There is a reason ISP like fast.com can give nice and high results well beyond what is possible over TCP/IP layer and its use of Netflix CDN means for a big ISP will often be on-net

It was the fibre you would have no connection i.e. FTTP is link at full 2.4 Gbps or nothing.

Needs you to post some links to the shared results from https://www.thinkbroadband.com/speedtest

I'll update a speedtest run on the main site, just tried

fastnet, 93mbps
ookla : 94mbps
bt wholesale: 90mbps
broadbanduk: 92mbps

If you can create an Ubuntu stick and boot your PC from that, then directly connect into the ONT. Run a few tests at different times of day.

All good suggestions from you all and I will give them a go if Openreach cant find an issue their end

In reply to a post by MikeBUK:

I'll update a speedtest run on the main site, just tried

fastnet, 93mbps
ookla : 94mbps
bt wholesale: 90mbps
broadbanduk: 92mbps

Hmm, that looks suspiciously like the ethernet port has negotiated down to 100Mbps (which has a maximum TCP throughput of about 94Mbps with an MTU of 1500).

If you are doing a direct PC-to-ONT connection, then you can check the actual link speed in your interface settings. You could also try putting an ethernet switch in between your router's WAN port and the ONT, and looking at the link speed lights.

Negotiating down to 100M is generally caused by a bad connector or cable. 100M ethernet only requires four of the 8 pins to be working (from memory it's pins 1, 2, 3 and 6), so if one of the other pins is broken or disconnected, the link can work at 100M but not 1G. It could also be intermittent - wiggling the cable might make a difference.

It could also just be a faulty ONT, like a dry joint on the board. Someone on the forum had their ONT fried by lightning coming in through the mains power supply; from then on it was working at 100M but not 1G. However if you've had an engineer visit, it probably rules that out.

Yep agreed, but if that’s what your ISP would like you use, it might add grist to one’s mill if you need to demonstrate an issue to them.

In reply to a post by candlerb:

It could also just be a faulty ONT, like a dry joint on the board. Someone on the forum had their ONT fried by lightning coming in through the mains power supply; from then on it was working at 100M but not 1G. However if you've had an engineer visit, it probably rules that out.

That was me, but the surge/spike came into the ONT via the network port, hence why it was crippled at 100M (along with a whole bunch of other network stuff that was copper connected, similarly totally nuked or somehow non functioning on the network side. Expensive lesson)

Easy to check if its WAN link to the ONT. The Smart Hub on the Status page will report the Ethernet connection speed - needs to be 1000 Mbps but the theory something is limiting down to 100 Mbps looks reasonable on data seen so far.

Could it be a dodgy ethernet cable, or maybe its plugging into the port?

In reply to a post by Pheasant:

That was me, but the surge/spike came into the ONT via the network port, hence why it was crippled at 100M (along with a whole bunch of other network stuff that was copper connected, similarly totally nuked or somehow non functioning on the network side. Expensive lesson)

How expensive? My lightning strike costs are probably approaching £20k ... yes, twenty thousand.

I had one bit of gear I use a precision GNSS receiver, a Leica GR50 that is worth roughly £15K on its own. Had to go back to Switzerland for surgery. They had to replace the network board and it’s still not totally right.

The full list of damage (throw away) included
- CradlePoint router
- 4 Netgear smart pro switches + SFP modules
- Gigaset DECT base
- Ring Doorbell
- 2 gate control motor drives
- gate control unit/logic board
- 2 smart gate interface units
- backup generator control panel
- mains fail transfer switch control panel

Some of the gear we had was blown apart like a grenade. Most other stuff completely blackened. A pair a stacked LAN switches spot welded their own chassis. Never quite seen anything like it. My electricians (who had 3 similar call outs for the same event) said our was one of the worst they’d seen.

Seems odd that both ONT and SmartHub have both already been replaced. You’d have to be really unlucky to have busted gear in succession. That really only leaves user equipment / patchleads or indeed something further upstream.

I am "glad" that someone else has a similar level - people don't seem to believe figures of £10-20k when there is no structural damage.

I had a Cisco switch - with a hole cut through te case, my Gigaset N300A was just pieces of plastic, BT master socket, casught fire but use of self extenguising plastic stopped that. PC and docking station, plus second dock, HDL lighting (still awaiting final work), RCD in the CU and more.

and the gold star goes to you

I resisted swapping them out as BT always do the "Is the red cable in the box routine", engineer turned up and I said the only bit not checked so far is the cable, new one put in and bang 300 mbps

Ouch! Yes the destruction needs to be seen to be believed. I was told east anglia is a lightning hotspot. This map and experience doesn’t argue with that!

due a rather big storm tomorrow, you have all been warned (I live in middle of Norfolk)

In reply to a post by MikeBUK:

and the gold star goes to you

I resisted swapping them out as BT always do the "Is the red cable in the box routine", engineer turned up and I said the only bit not checked so far is the cable, new one put in and bang 300 mbps

Oh dear. Probably the first thing that should be checked. People assume new patch leads are all good an created equal. Fact is the vast majority really aren’t that good at all and there are plenty of duff ones about.

Now being on full FTTP including voice removes one potential route in. Storms forecast for tomorrow, but without hitting the main switch how do you protect everything? Dishwasher was one oif the items last time.

Out of 10 houses here, at least 7 had problems and one unoccupied. In a nearby close 5 from 7 ... we were the worst.

Urghhh. It’s “the season” and we’re having perfect weather for it. Murphy stay away!! 🤣

I now keep boxed spares of the most critical kit. When you need it most you don’t have it. Next day delivery is a bit hit and miss these days with stuff in short supply and long lead times.

good new for old policy, blowtorch, cheap graphics card you can abuse with blowtorch, and fill the form in stating it was a 3080ti (This is a joke not a suggestion, honest)

In reply to a post by MHC:

Now being on full FTTP including voice removes one potential route in. Storms forecast for tomorrow, but without hitting the main switch how do you protect everything? Dishwasher was one oif the items last time.

Out of 10 houses here, at least 7 had problems and one unoccupied. In a nearby close 5 from 7 ... we were the worst.

Fact is you really cannot. I’ve tried to minimise the risk as much as possible within budget. Unfortunately any external cabling acts like an antenna for ground potential difference. So you can still get done without a direct strike. Ive tried to mitigate by fitting proper Type 1/2/3 surge arrestors now on the incomer mains as well as all external power legs at the far ends.

My electricians have a theory that it’s made worse with the typical PME (TN-C-S) service connections. The older TT connections with local grounding were better in this respect. Who knows.

In reply to a post by MikeBUK:

good new for old policy, blowtorch, cheap graphics card you can abuse with blowtorch, and fill the form in stating it was a 3080ti (This is a joke not a suggestion, honest)

🤣🤣

In reply to a post by MikeBUK:

and the gold star goes to you

I resisted swapping them out as BT always do the "Is the red cable in the box routine", engineer turned up and I said the only bit not checked so far is the cable, new one put in and bang 300 mbps