BT DNS issue

Last weekend, I saw an issue where a domain was resolving to apparently the wrong IP address. Using pi-hole and google's DNS servers, the problem vanished shortly after for me.

However someone who was accessing via a BT connection and using BTs homehub & DNS in a very standard (out of the box) approach is still seeing incorrect DNS resolution.

Can someone check to see what mail.dorsetiam.org.uk resolves to via BTs DNS? It should point to 77.72.0.130

I've tried an ipconfig /flushdns on their machine (via Quick Assist) and that didn't help. nslookup returns the wrong IP (I didn't make a note of what it was), on their machine.

Thanks

That's how it resolves for me, currently using ISP assigned dns servers.

From my own DNS resolver:

Text
1 23 45 67	C:>nslookup mail.dorsetiam.org.uk Server:  pfSense.localdomain  Non-authoritative answer:Name:    dorsetiam.org.uk Address:  77.72.0.130Aliases:  mail.dorsetiam.org.uk

Pi-Hole and Unbound.

In reply to a post by mbames:

Last weekend, I saw an issue where a domain was resolving to apparently the wrong IP address. Using pi-hole and google's DNS servers, the problem vanished shortly after for me.

However someone who was accessing via a BT connection and using BTs homehub & DNS in a very standard (out of the box) approach is still seeing incorrect DNS resolution.

Can someone check to see what mail.dorsetiam.org.uk resolves to via BTs DNS? It should point to 77.72.0.130

I've tried an ipconfig /flushdns on their machine (via Quick Assist) and that didn't help. nslookup returns the wrong IP (I didn't make a note of what it was), on their machine.

Thanks

i get this ip 81.17.29.147 using DNS crypt (mail.dorsetiam.org.uk ) But 77.72.0.130 for dorsetiam.org.uk Just re-tried and now get 77.72.0.130 for both

Edited by tommy45 (Tue 07-Jun-22 19:59:51)

Typical Plusnet DNS server (212.159.13.49) -> 77.72.0.130

CNAME mail.dorsetiam.org.uk dorsetiam.org.uk
A dorsetiam.org.uk 77.72.0.130



Ditto for opendns, google et al. I can't get any sensible response at all from trying to use any of the alleged BT DNS Servers but that could simply be because I'm technically not on a BT connection and don't have a BT allocated IP.

Tracing route to mail.dorsetiam.org.uk [63.141.242.45]

From BT using their DNS

Yep I know we are talk about MX records and it A records IP numbers.

https://www.whatsmydns.net/#A/mail.dorsetiam.org.uk

It seams to show 63.141.242.43 / 77.72.0.130 / 81.17.18.197 / 192.187.111.221

I can get different things off loads of different servers (I am on BT). It's not an A record, it's a CNAME, and I've seen Google's DNS servers return:

77.72.0.130
63.141.242.44
81.17.18.197
81.17.29.147

Sometimes it returns an A record with no sign of a CNAME. It doesn't look like it's just a BT issue either:
https://www.whatsmydns.net/#A/mail.dorsetiam.org.uk

RIPE seem to also think there are problems

https://stat.ripe.net/widget/dns-check#w.resource=do...

That looks like the IP I saw earlier via the BT connection (and quite possibly the one I briefly saw on my setup on Sat).

I'm confused as to how this could have happened. None of the other domains which are configured the same way (Fasthosts and Krystal nameservers) have suffered the same fate.