[dns-operations] nscd issue

Mohamed Lrhazi ml623 at georgetown.edu
Thu Oct 4 19:17:55 UTC 2012


Sorry for this off topic question and please do point me to a more
appropriate list if you know one.

I was trying to understand the source of some unusual traffic from one of
our hosts... It was running some python script that needed to constantly
resolve two names ... turns out nscd was not liking those two names and not
caching them!

After many tests, we are thinking that nscd does not cache a name that
returns more than one IP address! Could that be true? Is that expected and
known behavior of nscd?

I noticed what follows:

- For an entry corresponding to a single A record, the log shows it added
two entries for: GETHOSTBYNAMEv6 and GETHOSTBYNAME
"getent hosts" commands result in the latter entry being used.

- For an entry corresponding to a multi A record, the log shows it added
just one entry, the one fore GETHOSTBYNAMEv6
"getent hosts" commands result in a "have not found hosts entry" log and
DNS queries being made.

Thanks a lot,
Mohamed.
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