Lost 'parts' of the internet due to BT DNS issues

[lostintranslation]

Mostly everything is fine. Google / Netflix / email / Amzon Prime / etc etc.
But we have lost access to: Whatsapp / Strava / Slack / FB / some universities / loads of https sites / some other social media / iMessage / etc .
Sometimes; overnight the internet world gets re-set and all is perfect ...... but only for 24/48 hours 😞
Have new hub router /  all security and controls are off / no firewall / no anti-virus.
Everything and all devices work fine on cellular.

Have read that this is all a BT DNS server issue?? Since January 2024?? 
Kids forced to use VPN's, including for school work

Is there way to change the BT DNS?

[david2609]

I've got the same issue after being fine for a month (as a new customer) the issue started on 10th September for me.

I think I've whittled it down to a DHCP issue where previous IPs are not being released properly and it's breaking IPV4 connectivity for future devices and attempted connections until the whole lot is restarted.

My standard test has been to try and access google (which seems to always work) and try to access Reddit or the BBC website (which usually break). I've just done a test  with them working, and then temporarily disabled and then re-enabled my PC's network card. I am now currently unable to access the BBC website, but can access these forums and google. (Interestingly enough, I already tried bt.com and it directs to a different server than the community subdomain).

Doing ipconfig /all in a command terminal shows my IPV4 address as a duplicate. I also cannot access the router hub as of this moment (until I reset the thing or do some other experimentation.) Swapping from a static ip to automatic has it running up through IP addresses showing each one as a duplicate (seen by spam using ipconfig /all and watching it change). I suspect it will keep trying to connect through ips over and over and keeps putting them as duplicates until it runs out of addresses to pick from. Interestingly, though I'd have expected otherwise, choosing another static IP (which it doesn't signal as a 'duplicate') does not enable me to connect to all the problematic sites (bbc yes, but reddit no) but I can now access the router software. -> Note that after a few minutes, I am now able to connect to Reddit but NOT the BBC website, truly strange.

My networking knowledge is decent, but not massive in a practical usage sense. Whether this would be easily fixable on our end is not something I could confidently claim. I don't want to have to buy a separate router but it might end up being our only option unless BT/EE are able to push a firmware update.

[countrypaul]

@david2609 do any of the PCs, Pads, Laptops, Phones have MAC randomisation (private addressing) turned on? If so that can cause all the IP addresses on the DHCP server to be used up before they expire thereby causing issues. It is often best to disable the MAC randomisation when a device is linked to your own network.

If you are using a BT Smart Hub 2 the hub does not forget the DHCP addresses even on reboot and power cycling, the only way to clear them, I'm led to believe (I have an SH1) , is to perform a reset back to factory settings.

[countrypaul]

@lostintranslation having reread your post could you have any devices that are using MAC randomisation and causing DHCP issues as a result (see above post or @david2609 ). If you end up with more than one device having a given IP address then it can become very hit and miss as to when some things work.

[david2609]

I had already turned mac randomisation off on all of the relevant devices prior to doing my disable/enable test. This PC has no such feature (can you even DO mac randomisation with an Ethernet?) The next time I feel like testing (I have other things to attend to at the moment) I'll compare mac addresses to see if they are changing.

A factory reset via the hub software did not stop the problem from occurring, I'll try the hardware reset later.

[david2609]

As I was writing this my connection 'half-dropped' (I suspect something left the network and rejoined) while I was connected to the hub software. Checking down the devices list I've noticed that there is a 2.4 wifi that uses the same IP as this computer but using a different mac address. Changing the ip on this computer, also changes the ip for the 2.4 wifi 'device' (I was able to see this change by connecting to the router using the ipv6 unicast).

This PC is ethernet only, so it would appear as though the router is trying to create both an ethernet and a wifi connection at the same time which causes the DHCP conflict. Authoritative DHCP has no effect on or off and I am unable to 'Remove' the devices because for some reason completely beyond understanding, you cannot remove connected devices. As there is no MAC filter on this router—again, something completely beyond understanding—I cannot set an allow/block list to only allow specific addresses (and thus blocking the 'dummy' wifi). But regardless, that is besides the point as it appears to be the core DHCP server that is the problem. Turning off wifi (sorry everyone else), removing the conflicting 'device' and then turning it back on seems to fix it by confirming the assignment to my ethernet only, temporarily at least.

(this is in a new post because I ran out of time while editing the previous one while doing some investigating and it will not allow me to change it any more)

[lostintranslation]

Thx all - but it appears that "we" as in "me" need to do the work here. Either change the router; change settings, re-set or re-start, etc, etc.

Broadband needs to be plug and play - period. I'm on my 3rd BT hub - they tend to just send you a new one and hope that it works 🤔....but never does.  And to be fair to BT we never had any issues for years and years - its only the last 6 months or so.

So whatever has changed it has changed at the BT end - I just wish the customer service dept had access to a senior enough engineer to resolve the problem....they are as perplexed as I am!