[syslog-ng] Resolving Hostnames for Syslog Source IPs

[Sawall, Christopher L]

Thanks for the suggestions.  It seems that about 10 out of 50 of the
devices did not have the proper PTR records.  Adding this has resolved
my problem.

Thanks,
chris


-----Original Message-----
From: syslog-ng-bounces at lists.balabit.hu
[mailto:syslog-ng-bounces at lists.balabit.hu] On Behalf Of
Valdis.Kletnieks at vt.edu
Sent: Wednesday, June 01, 2005 3:53 PM
To: Syslog-ng users' and developers' mailing list
Subject: Re: [syslog-ng] Resolving Hostnames for Syslog Source IPs 


On Wed, 01 Jun 2005 09:33:58 PDT, Jarrod Manzer said:
> I had this same problem. I resolved it by logging by IP and then doing
> reverse DNS lookups with a script and creating symbolic links to those

> IP based directories. The end result was people who like to use IP or 
> DNS were happy. Gotta make sure your reverse is set up properly
though.
> 
> But I never did find out why syslog-ng couldn't resolve the same names
> that the host command on the same box could.

The most common cause for things like this is semi-borked DNS that
*appears* to work, but in fact is subtly misconfigured.

A few things to check:

1) Take the IP address, and look up the PTR, which should give you a
hostname (this is where most 'host' commands stop). Then actually check
that hostname in the DNS, and make sure the IP is listed in an A record
(some resolvers do this additional sanity checking).

2) You may have a "lame delegation". Look at the SOA and NS entries for
your DNS zones, both PTR and A, and double-check that all machines
listed in NS are in fact serving up correct data for the zones (a quick
double-check is if all the DNS servers show the correct zone serial
number in the SOA). It often happens that if there are multiple NS
records, a daemon will "lock in" on asking one NS first, and if it
returns an authoritative NXDOMAIN because it's a lame delegation, the
daemon won't ask other NS.  However, when you use the 'host' command, it
may check some *other* NS entry first and magically appear to work.

3) Double-check /etc/resolv.conf to make sure it points 'nameserver'
entries at DNS servers that pass the sanity checks in (1) and (2)....


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