[PLUG] Spotty DNS Resolution

Daniel Hedlund daniel at digitree.org
Sat Oct 14 22:44:20 UTC 2006


I am trying to track down the cause of some spotty DNS service, which 
has recently started causing me to lose emails from some people.

My DNS server seems to work fine in itself.  I'm using BIND 9.3.2.  I 
can use nslookup to query every single hostname in my zone file when I 
point the queries at my nameserver.  I can do this locally on the box 
that has BIND, from any other machine on my local network and from 
computers on the "outside".  I haven't tested enough from the outside 
yet to know for certain.  My DNS configuration seems fine and it is the 
same configuration files I used to use a year ago without any problems 
and the service responds as I would expect.

The problem then is that some DNS servers on the Internet get the 
correct DNS information from my server while others don't.  Sometimes 
the DNS server will get some of my DNS records but not all of them.  I 
have not updated my DNS records in a couple of months so it's not an 
issue with propagation time.

I'm using Dotster as my registrar and they require that I provide two 
fully qualified hostnames for my DNS.  I only have one DNS server so I 
provide the registrar with a hostname that doesn't have a DNS server on 
it, using another static IP address I own, but not on the same network.

I'm using DSL-Only as my ISP with a static IP address.  I have a Linksys 
WRT54G router that is set to forward all DNS requests to my nameserver; 
I am not using OpenWRT on this box, but  rather just the standard software.

To do some testing, I contacted two of DSL-Only's DNS servers, 
sulfur.dsl-only.net (63.105.16.4) and silver.dsl-only.net (63.105.16.2). 
  sulfur is able to correctly provide me with information for all of my 
DNS entries.  silver, on the other hand, can only provide me with 4 of 
about 13 records and returns failure on the other 9, including failure 
for my MX record.

Throughout my period of DNS woes, I have been receiving email from all 
of my mailing lists without any major hiccups.  I have been able to 
communicate with many companies in a timely fashion who have their own 
mail servers and have not noticed any missed communications (no 4 hour 
delays, etc).  Rich Shepard and one other individual written to me about 
problems DNS resolution problems from their end using public nameservers 
(Rich, care to elaborate?).  Google's Gmail used to work but now doesn't 
work for sending email to my address.  I'm still waiting for Gmail to 
report back an error message.  I haven't tested Yahoo or Hotmail.

My DNS server is authoritative and is the first entry in my list of DNS 
servers with my registrar.  It's not something silly like using a 
possibly unresolvable hostname, as I have entered a hostname that is not 
managed by my DNS server itself (ie. subxx-xxx.member.dsl-only.net.

I'm wondering if my Linksys router is to blame.  I might put OpenWRT on 
it in the middle of the night tonight if nobody else can offer up any 
suggestions (I have my configuration settings all ready to go from 
another Linksys box I had).

Any thoughts on where to start?

Cheers,

Daniel Hedlund
daniel at digitree.org



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