This topic

DNS Issues

csalmeida — Wed, 31 May 2023 10:36:33 GMT

Hi,

I am a developer working with CWM Environmental and the team has reported they cannot see the new version of the site at cwmenvironmental.co.uk

Users at the office (with internet provided by BT) either end up at the old IP address (old version of the site) or see a "page can't be reached" screen. Everywhere else the new site can be visited with no issues.

I have also issued a request for their IT department to look into reseting their router(s) but this didn't yield results unfortunately.

Initially, I thought this could be a DNS propagation issue but that has completed a while ago and since the issue didn't go away and since the site is accessible out of the office with other ISPs. Could be a cache that is stale on BTs side since users with other ISPs can visit the site?

If that can be the case, how can I contact the network team to look into the issue please?
I am not a BT customer by the way I'm just trying to sort out an issue on behalf of a customer.

Thank you for your time, I hope to hear from you soon.

Re: DNS Issues

Keith_Beddoe — Wed, 31 May 2023 10:40:29 GMT

@csalmeida

This is just a customer to customer help forum, everyone here, including myself, are just customers.

The only BT Employees are the forum moderators.

Re: DNS Issues

csalmeida — Wed, 31 May 2023 10:43:13 GMT

Thanks Keith, in that case is there a way for me as a non-customer to contact BT directly for this sort of issue?

Appreciate the help.

Re: DNS Issues

Crimliar — Wed, 31 May 2023 17:34:59 GMT

Someone would need to verify this, but I cannot see any DNS propagation issues with the site on IPv4, but from what I can see anyone on a pure IPv6 network is not going to the site at all - anywhere, not just from BT!

Re: DNS Issues

gg30340 — Wed, 31 May 2023 18:38:43 GMT

@Crimliar wrote:

Someone would need to verify this, but I cannot see any DNS propagation issues with the site on IPv4, but from what I can see anyone on a pure IPv6 network is not going to the site at all - anywhere, not just from BT!

I can access the site no problem using IPv4. I don't have IPV6 only but suspect you may be correct.

Re: DNS Issues

csalmeida — Thu, 01 Jun 2023 09:07:41 GMT

@Crimliar thank you very much, I didn't think of this before and it might help.
I could enable IPv6 on the site and see if that fixes the issue.

Hosting support says:

After reviewing on our end, it appears that there is likely an issue with the route that traffic takes from your location to your Droplet. Could you share the following information to help us verify and troubleshoot this issue?
1. What is your public IP address? You can use http://whatismyip.akamai.com/ to find out if you're unsure.
2. Who is your ISP?
3. The MTR (with 'mtr -rwbzc100 x.x.x.x'), from yourself to the droplet.
4. The MTR, in the opposite direction from the droplet to your public IP address from step 1.

However, getting the team to go through this process and send the output might be challenging.

Re: DNS Issues

Les-Gibson — Thu, 01 Jun 2023 09:23:00 GMT

@csalmeida

@Crimliar is correct, an IPv4 ping confirms that the site has a valid IPv4 address but an IPv6 ping fails miserably stating that the host could not be found.

(ping -6 cwmenvironmental.co.uk from a Windows console) without the brackets

Re: DNS Issues

csalmeida — Thu, 01 Jun 2023 11:08:46 GMT

Thank you @Crimliar and @Les-Gibson.
Following your suggestion I've enabled IPv6, configured it and added AAAA records for the domain.

Do you see any changes on your side? Appreciate the help as this has been really challenging to debug on my side.

Ping output:

ping -6 cwmenvironmental.co.uk
PING cwmenvironmental.co.uk(2a03:b0c0:1:d0::35a:8001 (2a03:b0c0:1:d0::35a:8001)) 56 data bytes
64 bytes from 2a03:b0c0:1:d0::35a:8001 (2a03:b0c0:1:d0::35a:8001): icmp_seq=1 ttl=64 time=0.064 ms
64 bytes from 2a03:b0c0:1:d0::35a:8001 (2a03:b0c0:1:d0::35a:8001): icmp_seq=2 ttl=64 time=0.062 ms
^C
--- cwmenvironmental.co.uk ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 0.062/0.063/0.064/0.001 ms

Re: DNS Issues

licquorice — Thu, 01 Jun 2023 11:28:03 GMT

Accessible via IPv4, not accessible via IPv6 using Google IPv6 DNS servers. BT use IPv4 DNS servers for IPv6 addresses. Haven't tried using IPv4 DNS to IPv6 address as just disabling IPv4 in network adapter to force IPv6 connection.

Re: DNS Issues

csalmeida — Thu, 01 Jun 2023 12:06:12 GMT

Gotcha, this is super helpful thank you.

This means perhaps it's not that the broadband IP is blocked on the hosting side (like BT support suggested) as I'm assuming you, @licquorice and @gg30340 are BT customers and can access the site fine.

I wonder if this ends up being stable DNS cache at the router level and it needs to be cleared in order for the domain to resolve to the right IP. 😅

Re: DNS Issues

Les-Gibson — Thu, 01 Jun 2023 12:06:35 GMT

Pinging cwmenvironmental.co.uk [2a03:b0c0:1:d0::35a:8001] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 2a03:b0c0:1:d0::35a:8001:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Pinging cwmenvironmental.co.uk [2a03:b0c0:1:d0::35a:8001] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 2a03:b0c0:1:d0::35a:8001:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Re: DNS Issues

Crimliar — Thu, 01 Jun 2023 17:18:08 GMT

Actually checking IPv6 accessibility is more convoluted than you might think at first - I didn't want to sound like an old fart lecturing...

Anyhow before even bothering to do a deep dive, sites such as https://dnschecker.org/ are a great way to check on DNS propagation in general and over IPv6 (AAAA records). Most times IPv6 has ways to fall back to IPv4 compatibility if needed. Oh and running the "IPvFoo" Chrome extension can also help! I still can't perform an IPv6 ping on the address, but other than that it all seems easily accessible. *I can test this using more than one ISP, and I'm not seeing any difference between BT and Virgin.

Re: DNS Issues

csalmeida — Thu, 01 Jun 2023 17:25:56 GMT

Not at all @Crimliar, please lecture away, it's helpful.

What a strange issue, at this point I don't even think it's IPv6 because the office can access other sites with the same hosting solution that do not have IPv6 enabled.

It's reported that team members when in the office network either get redirected to the old IP and end up seeing a previous version of the site or get "page can't be reached".

I'll keep investigating if I do find out what the issue is I'll update the thread.

Can't thank you all enough for the help so far.

Re: DNS Issues

csalmeida — Mon, 19 Jun 2023 08:56:59 GMT

It turned out that the location where customers could not access the site had an internal configuration that would resolve itself to the previous IP.

Thank you for the help, everyone.