How does DNS monitoring work?

What is actually monitored?

We monitor the site you added to Oh Dear account - we do not attempt to find all DNS records under a domain.

If your site is "domain.tld" but want to be notified for DNS changes to "secret.domain.tld" or "very.hidden.subdomain.domain.tld" you will need to add each site separately to your dashboard to monitor it.

How does it work?

We use our ISPs' nameservers to resolve the DNS queries, which is a combination of Vultr/Digital Ocean. We don't cache DNS records on the client-side, so perform a fresh DNS query for every uptime check, to mimic a "new user" querying the site.

We actually query: root -> intermediate -> domain nameservers.

If there are sudden spikes in performance, it could be due to any of them having to retry but we don't yet show this on the graphs so it's hard to see why some DNS requests are slower than others. 

It also isn't uncommon to get a spike in there, as sometimes a nameserver just takes a bit longer to reply (or a packet gets lost on the way).

Note: the ISP's nameserver could also be caching the results on their nameservers.

You find more details in our dedicated DNS monitoring documentation.

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