I have fibre broadband (not Virgin, so not all fibre). I have one PC connected to the router via cable, and a tablet, a phone and a laptop which I connect wirelessly. For a year or more all has been right. Now, having been away for a couple of weeks I’ve come back to find that the phone, laptop and tablet are very slow when connecting via wi-fi. The odd thing is that this is only the case when the wired desktop PC is switched off. Once it is switched on the wireless devices are up to speed! Any ideas what is going on? DNS?

Is the internets/wifi slow or is it taking a while for the devices to connect to the wifi?
The former sounds like DNS while the latter sounds like it’s taking the router a while to assign DHCP addresses.

Have you tried turning it off and back on again?

@sharkbait the former. Wifi is sloooow. Youtube is just a blue doughnut, other things take yonks.

@cougar as an IT professional I followed my own advice (for once), so yes.

Try unplugging the desktop from the router whilst it is off and see if it makes a difference?
There were issues a while ago when specific network cards on specific drivers would send out broadcast storms when in a powersave / suspended state

Wifi is sloooow.

…. but the wired PC is fine? Tried changing wifi channels?

Try unplugging the desktop from the router whilst it is off and see if it makes a difference?

I’d be curious to see the outcome of this also.

When you say it’s fine when the PC is on, do you mean up with Windows (presumably) running, or is merely the act of pushing the power button enough to immediately fix it?

Try a tracert www.google.co.uk in both working and symptomatic scenarios and compare the two, it might help isolate what’s going on here.

I’ve tried it with the PC on but unplugged from the router and the problem is present. Connect the PC to the router and all is good. @Cougar the PC needs to be switched on and given a bit of time, presumably to load windows.

Changing channels has been suggested by the ISP support, but my router doesn’t have this facility, so I’m waiting for them to send me a newer router. If this turns out to be solution, why would this problem appear after a few years?

Shot in the dark but,

The PC has a wireless NIC. The wired connection has developed a fault, meaning that the WiFi NIC is suddenly taking precedence and it’s 802.11b or some such pulling the entire wireless network down. Solution, disable the wireless NIC and / or replace the Ethernet cable.

I have one PC connected to the router via cable

Connect the PC to the router and all is good.

Which is it?

Shot in the dark but,

The PC has a wireless NIC.

Apparently not, but good thinking.

I have one PC connected to the router via cable

Connect the PC to the router and all is good.

Which is it?

Normally the PC is connected to the router. For test purposes I disconnected the PC while it was on. The PC has to be on AND connected, in order for the wireless to perform normally. If it is either off, or simply disconnected, then the wireless is so slow that things don’t connect or take ages.

I’ve since tried changing the channel on the router to 6 (from auto) and things seem much improved, though I’ve no idea why.

improved, though I’ve no idea why

USB 3 allegedly interferes with 2.4 GHz WiFi??
Edit: Doesn’t explain the PC on/off thing tho

That is an odd scenario!

Does the WiFi improve if you hard wire the laptop? i.e. desktop off and unplugged, laptop wireless disabled, laptop cabled in using the same cable and router port that the desktop normally uses.

Have you tried unplugging the desktops cable from the routers port whilst the desktop is off? Or does using a different cable and/or port on the router make any difference whilst the desktop is off.

I would suggest a factory reset of the router

You could try assigning a static IP address [and gateway, etc] to one of the wireless devices and try it with the PC disconnected.

[longshot]
Did you configure the router with some weird software on the PC which the router is looking for?
[/longshot]

It’s a long shot but I think I would be comparing the network settings for both wired and wireless connections on the devices in case the wireless devices have been assigned your wired computers ip as a gateway or something stupid like that.

I was just going to post pretty much what DM52 did. I reckon somehow the wired PC has ended up being the gateway or DNS relay for the network (or something like that). Check the IP of the PC, then see what the wireless devices have configured as the GW/DNS IP addresses.

I reckon somehow the wired PC has ended up being the gateway

I thought about this but decided that the wireless devices simply wouldn’t connect to the internets at all if the gateway couldn’t be found [as there’s no backup gateway address].

This is one reason why I suggested a traceroute earlier (which hasn’t been done yet as far as I can tell).

I’m very much an amateur but could it be something like the DHCP or ARP cache on the router not working properly, and the router having to continually re-establish IP address to MAC, but the PC has a working ARP cache which the router can use?

I reckon somehow the wired PC has ended up being the gateway or DNS relay for the network (or something like that).

This is the sort of thing I was thinking, without having any idea of how it might work. The PC is somehow involved in the wireless connection.

To answer some other questions the router is as configured out of the box. I did run a traceroute but I don’t know what I’m looking for. Do I run it from the PC?

Has the wired computer, assuming it is a Windows based PC, somehow got internet connection sharing enabled?

What dns are you using? Try a different one?

Yep, on the router see what’s entered as the DNS server – and change it to 8.8.8.8 (Google’s own) if it isn’t already!

Well the new router (with 5GHz band) has arrived and been installed. And all is working well, so despite the temptation to get to the bottom of what was happening I’m going to leave it at that.

Thanks everybody for all your input, and I’ve learned a few new things about networks from the hive mind.

Damn it, we needed to know!

I did run a traceroute but I don’t know what I’m looking for.

Yeah, but we do. :-p

see what’s entered as the DNS server – and change it to 8.8.8.8

On this, have a look at https://www.quad9.net/ – it’s a public DNS a la Google, at 9.9.9.9, but claims to filter out known hostile / malicious sites.

1.1.1.1 (Cloudflare) is handy to know too – it claims to be the fastest DNS in the world, and doesn’t log your IP address.

interesting….. and yes….. damn it! Put the old router back on and get us some answers 🙂