RE: Sendmail/DNS Wackiness.

["Jay Benfield" <jay@xxxxxxxxxxxxx>]

Adam -

Good call! You were right regarding the nslookup stuff.

I should have caught that *duh*. I guess I was thrown
off course because I did an nslookup from the server
resolving IP > name, and it worked. So I just breezed
over it.

So, if reverse lookups are functioning locally, but
not remotely, what's going on? Is it simply not
propagating?

It seems like I had this problemo a while back, but
I don't recall how I corrected it.

- Jay

-----Original Message-----
From: Adam Williams [mailto:awilliam@whitemice.org]
Sent: Monday, September 13, 1999 6:26 AM
To: klug@klug.armintl.com
Subject: Re: Sendmail/DNS Wackiness.


> I was not involved in the installation process, but called in after
problems
> started occuring. She had attempted to get everything going using a couple
> different X windows GUI tools - to no avail. I have a fundamental distrust
> of all of the handy x utils, maybe I'm odd :-)

Good, an Admin needs to know WHY things work the way they do,  not just how
to
make it happen,  and all the GUI tools hide the WHY.


> <!-- SNIP SNIP -->
>
> ----- Transcript of session follows -----
> 550 <jay@carrinter.net>... Host unknown (Name server: (IP ADDRESS OF
HOST):
> host not found)
>
>     [ Part 2: "Delivery Status" ]
>
> Reporting-MTA: dns; DOMAIN.COM
> Received-From-MTA: DNS; DOMAIN.COM
> Arrival-Date: Sun, 12 Sep 1999 19:49:48 -0400
>
> Final-Recipient: RFC822; jay@carrinter.net
> Action: failed
> Status: 5.1.2
> Remote-MTA: DNS; IP ADDRESS OF HOST
>
> <!-- END SNIP -->
>
> It should be noted that mail CAN be received from outside sources and can
be
> sent to local users. I can also do nslookups from the machine using the
> local name server. Server's resolv.conf is set to look at itself - all
> secondary NS stuff has been removed temporarily for testing purposes.
>
> I really believe it's something to do with DNS BUT...

I agree.


> ... restarted named & sendmail many, many times after trying many, many
> things :o)
>
> In /var/log/messages I had this message a couple of times:
>
> Sep 12 19:29:35 SERVERNAME named[9387]: ctl_server: bind: Address already
in
> use

This means an copy of the given service is still running when you tries to
start it.

>
> I'm not sure if that's related.
>
> Any help on this matter would be greatly appreciated. I've got several
> RedHat 5.2 servers up and running, and I've pretty much duplicated their
> configurations - not sure what I'm missing (if anything).


When A recieves a message from B,  it looks up B's IP address to see that it
is
really B, that is that the name B claims is B's actual name in DNS.  A
server
failing to lookup B.  Point you nslookup at a DNS server outside your
organization and try to lookup your server.  If your machine is A.B.COM try
something like "nslookup a.b.com ns.staticky.com" and see if the DNS server
ns.staticky.com is able to find a.b.com.  And due the reverse with your IP
address to see that the remote DNS server can turn the IP into a name,  both
need to work before modern sendmail's will let you swap messages with them
 (I'll wager the first works and the second doesn't).