DNS lookup delays

From: Michael Grant (usenet-poster_at_Michael-Grant.me.uk)
Date: 09/25/03 

Date: Thu, 25 Sep 2003 21:33:11 GMT

I have a problem on my machine running Red Hat 7.3 that I think might
be caused by DNS lookup delay, but could do with a little bit of help
to get it sorted out. Despite having a ADSL connection at home,
fetching mail from POP3 servers trickles in at narrowband rate.

The fetchmail FAQ says long delays near the start of each poll cycle
are caused by sendmail's hostname lookup when starting up and for each
HELO it receives in listener mode. As I also get a ten second delay
every time links carries out a name lookup, and having seen elsewhere
30 second delays for this reason with ssh, I suspect this to be my
problem. Though why this happens for sendmail and links, but not slrn
or mozilla I don't know.

I've tried consulting fetchmail and sendmail FAQs, and a wealth of
Linux FAQs and HOWTOs, and have got rather confused. Reconfiguring
sendmail not to do a lookup is one solution, but sounds like a
nightmare. Better to get to the root of the problem and cure the
delay (and reconfiguring sendmail won't help me with links).

The fetchmail FAQ continues:

   Your resolver configuration may be causing one of these lookups to
   fail and time out. Check /etc/resolv.conf and /etc/hosts file. Make
   sure your hostname and fully-qualified domain name are both in
   /etc/hosts, and that hosts is looked at before DNS is queried. You
   probably also want your remote mail server(s) to be in the hosts file.

Well, /etc/resolv.conf seems to be automatically generated on startup
and populated with the IP addresses of my ISP's nameservers;
/etc/host.conf contains "order hosts,bind", and /etc/hosts contains:

   127.0.0.1 localhost
   127.0.0.1 luminiferous.aethernet luminiferous
   127.0.0.1 localhost.localdomain localhost

I could try adding my POP server, but, again, that wouldn't help me with
links, and it doesn't explain why other processes have no problems
with name lookup.

Does anyone have ideas what's going wrong, and what I should do about it?

-------------------< Mchl.Grnt@luminiferous.aethernet >-----------------------
"Life is a multiple bluff; the object is to guess the | Roadrunner@
parity." - Paul Blain Levy | Michael-Grant.me.uk
-------------------< http://www.michael-grant.me.uk/ >------------------------

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