Re: DNS lookup delays

From: Robert M. Riches Jr (spamtrap42_at_verizon.net)
Date: 09/26/03 

Date: Fri, 26 Sep 2003 03:40:03 GMT

In article <slrnbn6noh.287.usenet-poster@luminiferous.aethernet>,
 Michael Grant wrote:
> 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.
>

If your delays are indeed caused by slow DNS servers, it
might help to some degree to enable a caching nameserver on
your local machine. That way, only the first lookup will be
slow. There was a long discussion in one of these
linux-related newsgroups within the past month or three
about the caching nameserver. With RHL 8.0, the caching
nameserver is actually an RPM, caching-nameserver-7.2-4,
which is a collection of configuration files for bind and/or
named. If it isn't available for RHL 7.3, you could
probably adapt the files from the 8.0 RPM fairly easily.

For the earlier discussion, see groups.google.com. Google
searches on the obvious terms is how I got enough
information to figure out how to run it myself.

Good luck.

Robert Riches
spamtrap42@verizon.net
(Yes, that is one of my email addresses.)

Relevant Pages

  • Re: Two domains, One Forest....
    ... (these are the DCs listed in DNS under the _sites area) ... However the delays are specifically related to MS products. ... > authentication as the user accounts and groups IAS references are also in ... >> This is not really a security group question, ...
    (microsoft.public.win2000.security)
  • Re: DNS or Smart host
    ... you need to fix DNS and identify the cause of the delays. ... your Smarthost could be seeing the same message delay ...
    (microsoft.public.exchange.admin)
  • SUMMARY: server-side ftp autorization delays
    ... I experience several-second delays when solaris 8 ftp server ... Clients are on LAN so it's not network speed issue. ... Delays seem to appear only for clients which are not in DNS. ...
    (SunManagers)
  • Re: server-side ftp autorization delays
    ... the /etc/resolv.conf on the server is ok, ... of the dns server is set correctly and dns is working ok. ... I experience several-second delays when solaris 8 ftp server ... Clients are on LAN so it's not network speed issue. ...
    (SunManagers)
  • Re: [opensuse] Default install creates /etc/.pwd.lock in 11.1
    ... some investigation it turned out that the delays are caused by nscd ... when user/group name lookup is done. ... but I haven't noticed delays the few times i have been able to run 11.1 ...
    (SuSE)