Troubleshooting erratic network performance

[John Sellens]

Oh oh - someone broke rule number one on you: no changes Friday
afternoon.

Could there be a DNS resolution problem? Could apache be trying
to do a reverse lookup on the IP address connecting and be timing
out?  Do the apache access logs show IP addresses or hostnames?
Can each DNS server in /etc/resolv.conf be reached and succeed
in doing a forward and reverse lookup?  e.g.
    dig @1.2.3.4 asbestos.ss.org
    dig @1.2.3.4 1.5.108.206.in-addr.arpa. ptr

Does the web page connect to a backend server e.g. mysql?
I had a slow page problem just the other week, because the
mysql server couldn't do reverse lookups on the IP of the
web server, which could be resolved either by fixing DNS
or adding an appropriate local entry to /etc/hosts.

You could watch DNS traffic and expect to see answers and
quick replies with tcpdump, if you know what interface to
watch.

Any idea what changed?

Hope that helps!

John
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