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  From: Adam Smith <adam.smith@sageautomation.com>
  To  : Dazz <bofh@afoyi.com>
  Date: Wed, 16 Apr 2003 09:36:33 +0930

Re: dns confusion

On Tue, Apr 15, 2003 at 11:44:38AM +0930, Dazz said:
> Adam,
> 
> > This is now also becoming a problem because our DNS server appears to have
> > cached the fact that i can't look up the host smtp01.seinf.abb.se.  This
> > is causing email to stop going to that host, and in particular one user
> > here needs to email that host with urgent information.
> 
> Is the name server caching the record or is it perhaps the MTA? Try using
> the 'host' command to look up the record:

The MTA (I expect lots of dropped jaws from this,) is on the Windows
platform at this time.  Using it's nslookup command I am still unable to
resolve the host.

> $ host -t any smtp01.seinf.abb.se [NAMESERVER.ADDRESS]
> 
> and see what comes back. If you get the correct details back, then it
> could be the MTA doing the caching. Try stopping and starting your MTA.
> When I try it I do not get any MX records back, but I do get an A record.
> When I look up the parent domain I get different MX records:

The remote mail host is es.abb.se, and the host command tells me that it's
MX's are:

# host es.abb.com
es.abb.com mail is handled (pri=10) by smtp01.seinf.abb.se
es.abb.com mail is handled (pri=20) by smtp02.seinf.abb.se
es.abb.com mail is handled (pri=30) by sdas01.seinf.abb.se

Running host -a tells me this:

# host -a smtp02.seinf.abb.se
Trying null domain
rcode = 0 (Success), ancount=1
The following answer is not authoritative:
The following answer is not verified as authentic by the server:
smtp02.seinf.abb.se     21425 IN        A       138.221.225.25
For authoritative answers, see:
seinf.abb.se    82528 IN        NS      dns6.telia.com
seinf.abb.se    82528 IN        NS      sdas01.seinf.abb.se
seinf.abb.se    82528 IN        NS      sdav01.seinf.abb.se
Additional information:
sdas01.seinf.abb.se     82528 IN        A       138.221.200.200
sdav01.seinf.abb.se     82528 IN        A       138.221.200.99

It tells me smtp02.seinf.abb.se is 138.221.225.25, and using dig I appear
to be able to resolve it, but not with nslookup.

smtp01 and smtp02 appear to point to the same IP address.  I'm confused as
to why nslookup is having so much trouble resolving this with our local
name server.

It's been about 20 hours since I looked at this yesterday.

bugman@jerome /home/bugman # nslookup smtp01.seinf.abb.se
Server:  jerome.sage
Address:  192.168.0.3

*** jerome.sage can't find smtp01.seinf.abb.se: Non-existent host/domain

bugman@jerome /home/bugman # nslookup smtp01.seinf.abb.se ns1.on.net
Server:  ns1.on.net
Address:  216.200.145.64

Non-authoritative answer:
Name:    smtp01.seinf.abb.se
Address:  138.221.225.24

> > I can not seem to purge the cache of our current DNS server, and it keeps
> > returning "Non-existent host/domain" when every other name server I try
> > can resolve the host name.
> 
> As others have said, doing a '/etc/init.d/named stop' and then
> '/etc/init.d/named start' should clear the cache (which is kept in memory
> IIRC).

Doing that has no effect.

> Also, is your nameserver a slave for the remote? If it is perhaps it's not
> pulling down the updated zone file. Stop the nameserver as above and then
> remove the zone file for that zone and start it up again.

I'm not quite sure what you are referring to, but there's no forwarders
section in my named.conf if that's what you mean.

After enabling the 'forwarders' section and specifying Internode's name
server, I'm suddenly able to resolve the host.  This still begs the
question as to why I have been unable to resolve it "on my own," without
the benefit of an upstream cache :/


-- 
Adam Smith
Information Technology Officer
SAGE Automation Ltd.

adam.smith@sageautomation.com
http://www.sageautomation.com

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