We have a client we host a web for (blog.foobar.es). We do not manage foobar.es's DNS setup, we just told them to point blog.foobar.es to our web server's IP.
We have noticed that sometimes we cannot browse to blog.foobar.es, but we can browse to other sites on that server.
Troubleshooting a bit using host(1) yields something funny:
$ host blog.foobar.es 126.96.36.199 Using domain server: Name: 188.8.131.52 Address: 184.108.40.206#53 Aliases: Host blog.foobar.es not found: 3(NXDOMAIN)
, being 220.127.116.11 one of Google's public DNS servers. However, sometimes the same server resolves the name correctly (!).
Another funny thing, is that our ISP's DNS servers sometimes say:
$ host blog.foobar.es 18.104.22.168 Using domain server: Name: 22.214.171.124 Address: 126.96.36.199#53 Aliases: blog.foobar.es has address x.x.x.x Host blog.foobar.es not found: 3(NXDOMAIN)
Which I don't really understand. I've dug around using dig(1), and have noticed they've set up a SOA record for foobar.es:
$ dig foobar.es ; <<>> DiG 9.7.0-P1 <<>> foobar.es ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59824 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0 ;; QUESTION SECTION: ;foobar.es. IN A ;; AUTHORITY SECTION: foobar.es. 86400 IN SOA dns1.provider.es. root.dns1.provider.es. 2011030301 86400 7200 2592000 172800 ;; Query time: 78 msec ;; SERVER: 188.8.131.52#53(184.108.40.206) ;; WHEN: Thu Mar 3 16:16:19 2011 ;; MSG SIZE rcvd: 78
... which I'm completely unfamiliar with.
We can't really do much as we do not control DNS, but we'd like to point our clients in the right direction...