Strange DNS Problem?

[Kevin Darcy]

Bigdakine wrote:

>Hi Folks,
>
>  I have this weird problem. I'm testing the fallover capability of our
>mailserver. I simply shutdown sendmail on the mail server, and start it in
>server mode on a backup mail server. The odd thing is that when I send mail
>from outside my domain to my domain, this is handled correctly. Running
>sendmail in verbose mode, I see it try the primary mailserver first, and the
>deliver the mail to the seconday mail server. Well, I gues that isn't odd. The
>odd part is, is that when I send email to other users within the domain, from
>within the domain, it chokes. It tries to deliver to "mailhost" and when that
>fails, doesn't attempt to deliver to the secondary which is akala. 
>
>mailhost is given a cname record is it is an alias for luna, the primary mail
>server
>
>
>My forward file looks like:
>
>; BIND version named LOCAL-020930.002038 Mon Sep 30 00:20:38 GMT 2002
>; BIND version root at akala:/opt/share/bind/src/bin/named
>; zone 'XXXX.COMM.GOV'   last serial 2004022920
>; from 150.70.102.225:53 (local 150.70.102.156) using AXFR at Sun Feb 29
>20:18:59 2004
>; TSIG verified: key luna-akala.
>$ORIGIN COMM.GOV.
>XXXX    86400   IN      SOA     luna.XXXX.COMM.GOV. stuart.XXXX.NOAA.GOV. (
>                2004022921 10800 3600 604800 86400 )
>        86400   IN      NS      LUNA.XXXX.COMM.GOV.
>        86400   IN      NS      AKALA.XXXX.COMM.GOV.
>        86400   IN      NS      HALE.XXXX.COMM.GOV.
>        86400   IN      NS      NWRNS.COMM.GOV.
>        86400   IN      NS      SERNS.COMM.GOV.
>        86400   IN      NS      MERNS.COMM.GOV.
>        86400   IN      NS      MWRNS.COMM.GOV.
>        2419200 IN      MX      5 LUNA.XXXX.COMM.GOV.
>        2419200 IN      MX      10 AKALA.XXXX.COMM.GOV.
>        2419200 IN      MX      15 HALE.XXXX.COMM.GOV.
>$ORIGIN XXXX.COMM.GOV.
>LUNA    2419200 IN      MX      5 LUNA.XXXX.COMM.GOV.
>        2419200 IN      MX      10 AKALA.XXXX.COMM.GOV.
>        2419200 IN      MX      15 HALE.XXXX.COMM.GOV.
>        2419200 IN      A       150.70.102.225
>AKALA   2419200 IN      MX      5 LUNA.XXXX.COMM.GOV.
>        2419200 IN      MX      10 AKALA.XXXX.COMM.GOV.
>        2419200 IN      MX      15 HALE.XXXX.COMM.GOV.
>        2419200 IN      A       150.70.102.156
>KUKINI  2419200 IN      A       150.70.102.143
>LEHUA   2419200 IN      A       150.70.102.145
>MOLOKINI        2419200 IN      A       150.70.102.158
>MIKI    2419200 IN      A       150.70.102.224
>MONKU   2419200 IN      A       150.70.102.157
>YANKEES 2419200 IN      A       150.70.102.147
>NENE    2419200 IN      A       150.70.102.227
>HALE    2419200 IN      MX      5 LUNA.XXXX.COMM.GOV.
>        2419200 IN      MX      10 AKALA.XXXX.COMM.GOV.
>        2419200 IN      MX      15 HALE.XXXX.COMM.GOV.
>        2419200 IN      A       150.70.102.221
>LULU    2419200 IN      A       150.70.102.219
>HAWAII  2419200 IN      A       150.70.102.149
>TYRKER  2419200 IN      A       150.70.102.140
>MAILHOST        2419200 IN      CNAME   LUNA.XXXX.COMM.GOV.
>PILIKIA 2419200 IN      A       150.70.102.222
>Q730R   2419200 IN      A       150.70.102.160
>KONA    2419200 IN      A       150.70.102.152
>EW      2419200 IN      A       150.70.102.169
>HOLO    2419200 IN      A       150.70.102.226
>KAKU    2419200 IN      A       150.70.102.218
>RAPANUI 2419200 IN      A       150.70.102.159
>KAIAPELE        2419200 IN      A       150.70.102.136
>EWA     2419200 IN      A       150.70.102.153
>
>Some things were changed to protect the innocent..
>
>Does anyone have any ideas on why local sendmail clients fail to deliver to the
>backup mail server?
>
The fact that delivery works as expected from the outside implies that 
there is no DNS problem here. Sounds more like a sendmail problem to me. 
It's fairly common for local domains to follow a different "code" path 
(i.e. different rulesets, etc.) than remote domains, especially if you 
have a "MAIL_HUB" defined.

                                                                         
                                                - Kevin