DNS_PROBE_FINISHED_NXDOMAIN : One of my domains cannot be reached by a mobile operator in Brazil (Operator name: TIM)

Using the TIM operator network (3G - 5G and Wi-fi TIM) in Brazil, it is not possible to access the domain and its subdomains. Already on Wi-Fi or any other 3G, 4G or 5G operator, live networks, of course, GTV, etc, it is possible.

This was detected from the 22nd of July 2023 (on a Thursday). We did this test on several devices in the state of São Paulo.

The subdomains and domains of may domain, in the TIM operator, are not in operation.

This is reducing traffic on our platforms. Apparently it’s a BGP problem, but I would like to know how to proceed?

You should contact the ISP and ask them why they are not routing to Cloudflare.

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They say I should talk to Cloudflare. :man_shrugging: :man_shrugging:
This has been going on for 5 days now

If everything works on all other networks, it points to an issue with the network it doesn’t work on.

DNS_PROBE_FINISHED_NXDOMAIN is a DNS resolution error, not a BGP error. It is probably unlikely that it’s a BGP error or tens of millions of domains would be inaccessible to end users.

So what testing was done from several devices? Simply an attempt to access the website? Did anyone perform a DNS lookup using dog or kdig? If so what was the ouput? Any other tests? Does DNS resolution work with a device which has different DNS specified?

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1 - So what testing was done from several devices?
Access tests by our users (access check), around 70 users of the operator reported the error. There were absolutely no reports of the problem prior to this fact.

2 - Simply an attempt to access the website? Did anyone perform a DNS lookup using dog or kdig? Any other tests?
I ran tests in two scenarios: A) On TIM’s network and B) outside TIM’s network.
A simple ping does not respond in scenario A. When switching to scenario B, it responds.
Tracert and nslockup cannot resolve the path.

3 - Does DNS resolution work with a device which has different DNS specified?
When changing DNS to 1.1.1.1 or 8.8.4.4 or 8.8.8.8 or known similar works without problem even connected in scenario A.

Other
I got a response from TIM (the ISP) and they informed me that ^there is a data difficulty in their region, it is already under treatment, I’m not very confident, but I’ll wait. And I keep them informed.

If DNS resolution works on other providers this is a DNS issue and since this provider manages their DNS I guess uh some diagnosis on failures could be passed here for the forums to :logo: DNS managers to see if there is an issue but L1 support at the ISP will need to pass on the ticket to an internal team and link to my comment.

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