[ale] Sendmail latency

[Ryan Fish]

> On Tue, 2005-01-25 at 00:59 -0500, Ryan Fish wrote:
> >  - The mail server is the only one experiencing the following issue with
the
> >  'host' cmd:
> >
> >  [root at mailserver mail]# host app01
> >  app01.clientdomain.com has address 192.168.3.0
> >  [root at mailserver mail]# host app02
> >  app02.clientdomain.com has address 192.168.3.0
> >  [root at mailserver mail]# host app101
> >  app101.clientdomain.com has address 192.168.3.220 (correct)
> >  [root at mailserver mail]# host app102
> >  app102.clientdomain.com has address 192.168.3.0
> >  [root at mailserver mail]# host mailserver
> >  mailserver.clientdomain has address XX.XXX.XXX.199 (the correct IP
address)
> >
>
> Based on the above data, you need to check the DNS server(s) specified
> in /etc/resolv.conf and determine why they are resolving app01 and app02
> as 192.168.3.0.  Secondly, you need to test the following:
>
>   # host 192.168.3.220
>   # host XX.XXX.XXX.199
>
> Verify that the above reports the correct reverse lookup for those IP
> addresses.


- Every server in the farm uses .219. 220, .221 and .222 for DNS however
none of those boxes have PTR records in place.  Is there a way to turn off
reverse lookups within Sendmail in hopes of it just accepting that the
messages sent from internal IPs are valid?  Otherwise, where would I add the
needed reverse records?

However, I don't necessarily feel as though this is an issue with Sendmail
as it was working fine (no complaints from the clients, no errors, etc.)
prior to my rebooting the app servers that double as name servers for all of
the boxes in the farm.  Each server was updated with Bind 9.2.4 Rel. 5_EL3
prior to the reboot (only thing DNS related I know of for sure).

>
> >  - I changed the domain names to protect the innocent...  The domains in
> >  question are valid though.
>
> Yes, but you left one valid IP address in there. ;-)
>
>
> > - How would I setup a caching name server on the mail server?  named is
> >  running on that box and named.conf contains info for each domain hosted
by
> >  the client however there I can find no other DNS info (as far domains
not
> >  hosted by the client) on this box but I have no idea where to look for
> > that.
>
> RHEL has a package called caching-nameserver, install it and you should
> be good.  FIRST backup your existing /etc/named.conf as well
> as /var/named/*.  Caching-nameserver will add a few entires
> to /etc/named.conf as well as a file or two to /var/named.
>
> I would also encourage you to look at running named inside a chroot'ed
> environment.  However that is a discussion for another day.  When you
> are curious just google for "chroot named".
>
> Assuming you have rndc all setup in /etc/named.conf, once you have
> things running issue this command: "rndc querylog" and then tail
> -f /var/log/messages to see how fast or slow DNS queries are being
> resolved.  Don't leave querylog enabled on a busy box. ;-)


- As these are production boxes not owned by me and I am as of yet still
unsure of myself in many ways when it comes to certain things I am going to
have to hold off on making a change such as this for now.

>
> -Jim P.
>
>
>
>
>