BT DNS not resolving certain addresses - e.g. www.aerobus.fr

[durks]

Using standard BT broadband at home, I am unable to resolve either of the domain names www.aerobus.fr  or aerobus.fr - the DNS lookup just fails. But those are valid domain names and, if I try to resolve them via my mobile network provider, that works fine.

This implies a problem with BT's DNS servers.

Do other people here see the same failure?

[Mod edit - removed hyperlink to website]

[gg30340]

The link work fine as does the domain name.

[durks]

Okay, thanks. I will investigate further to see if I find some local issue. It's definitely odd though - all other domain name resolution is working fine for me.

[durks]

I'm still puzzled by this - and I see the same problem on both Linux, and Windows.

Can you please tell me the IP addresses of the BT name servers you're using? Thanks.

For me, it's 81.139.56.100 (primary) and 81.139.57.100 (secondary).

[gg30340]

They are the same as yours, 81.139.56.100 (primary) and 81.139.57.100 (secondary).

[licquorice]

@durks do you have any parental controls enabled? They are network level controls and will be OS agnostic.

[durks]

Thanks for the suggestion.

I have not (knowingly, anyway) applied any such controls.

Logged into my router (a Smart Hub 2) as admin, I see the following note in the 'Access control' panel:

"Access controls are now managed using the app."

Sigh ... so I have now installed the 'My Bt' app on my phone. In that app, the only option for access controls appears to be a 'Control wi-fi access for your devices' section, and there is nothing active in that section.

Am I missing an explicit 'Parental controls' setting?

(BTW the PC on which I am typing this - and on which I first noticed the name resolution problem - has a wired network connection.)

I will persist in trying to debug my problem with 'dig' and friends and, if/when I make progress, I will post back.

Thanks.

[gg30340]

This may not help but you could try a factory reset on your BT hub. This will force an IP address change and restore all the settings on the hub. 

This will at the least give you a " clean page" to be working from.

[durks]

FWIW, this is now looking like a routing problem to me: I don't think I have functional routes to the specific nameservers.

The exact details - which depend on external configurations - are very difficult to diagnose, however ...

[durks]

By now, I am pretty certain that the cause of the problem I noticed (essentially, by chance) is a downstream IP routing issue caused by a configuration error in peering arrangements between ecritel.com and other network providers. Whether or not other BT users notice the same problem will  depend entirely on where they are located (it just depends on which particular routes any such users will be taking), and whether or not they are accessing related end services.

The full details are impossible for me to fully diagnose - but I would be interested to know whether or not anybody can suggest a suitable way to escalate the problem, in order to try to get it resolved.

Thanks.