DNS Monitor#20

A DNS monitor. Checks the returned IP of a query against an expected IP.

I see the advantage of checking against expected IP for an A record, but also just notifying on IP/record change (additionally). Also checking a DNS server for response time and failures, which is another interpretation of the description “DNS Monitor”

good idea

For me MX checks to know if clients Email is operational. We manage the Email system but sometimes the client is still responcible (or worse another 3rd party) for the domain and the DNS settings and on many occasions they make changes without knowing properly what they are doing. Getting some warning that the MX records have been altered would be awesome. I know other companies do this, but I would prefer to keep all my monitoring in one place. Many thanks.

We just had a failure where our DNS was broken and our web site was unreachable to users but UptimeRobot didn’t fail connection to the HTTP(s) servers.

Guessing that it was using a cached IP address.

@Dean altough this isn’t the best solution, in the meantime one could make a keyword check on dns query via dns.google, e.g. like https://dns.google/resolve?name=example.org&type=A

I think there are different scenarios that a DNS test should cover:

change from a specified value
any change, e.g. TTL, or change of the resolved value

But the URL method mentioned by @Felix to test DNS records is also very creative way to tacle this.

@Dean Keep in mind that the TTL may be the issue here as those cached records will continue to resolve, while the TTL is still valid. e.g. 24 hour TTL. The more important test here that you are describing is the DNS server is reachable, not the DNS records. If you can’t device a DNS reachability test, you could alternatively set a dummy A record with 5 second TTL. This might solve, if you cannot test your DNS server is reachable.

Good idea 👍

Unfortunately, it is not possible to check a DNS server correctly with Uptime Robot. Simply querying port 53 is not enough. I would find this an important function, as functioning DNS servers have an important function for the Internet.

mum, two years later – would be valuable tho

Incidentally discovered a client had moved their site. Notification of the A Record change would have been nice.

i have a dns server that checks port 53.
So far everything has been fine, but now it is constantly showing server down.
although i can resolve addresses perfectly from the server

does anyone have an idea what the problem could be?

If it’s behind a firewall check those logs. You might see the source IP is outside the whitelist of expected source perhaps. You could also do a packet capture.

no it is not behind a firewall

I had deleted it and created it again
Suddenly everything works again.
maybe i had forgotten to write https in front of the resolver. i don’t know.
it had been working for months now, but i’m glad that it finally shows operational again
when the response time comes in again, i don’t know if it will stay green……

Do you resolve by name or direct IP?

This one critical feature in web service monitoring. Other services usually allow dns server monitoring and which A record it returns.