[lug] DNS Problems: Is it me, or is it Comcast?

[Michael Deck]

I started having some DNS problems on Friday morning, and I need help 
determining whether it's in the name server that I administer, or whether 
it's entirely a Comcast problem (and what I might suggest they do about it).

Here are the details. On Friday morning I noticed I was unable to ping my 
remote server (cleansoft.com) by name but I could ping it by IP address 
(198.49.126.122). This from my home office, which has Comcast "business" 
cable internet. The remote host is running KRUD FC1 and is authoritative 
for cleansoft.com.

I also noticed I could ping the server by name from the host of one of my 
clients. At first I thought that this was a DNS refresh problem, or maybe 
an iptables problem, but I think I've convinced myself it isn't iptables.

If I put 198.49.126.122 in /etc/resolv.conf as a nameserver, my local 
problems go away. Emails appear to be reaching me from everywhere except 
other comcast users.

What I don't know is whether my zone files are somehow causing the problem. 
Here is another tidbit that worries me. When I use

   host -v -C cleansoft.com

from my client's system,

  > host -v -C cleansoft.com
  Trying "cleansoft.com"
  Received 121 bytes from xxx.xx.xxx.x#53 in 7 ms
  Trying "cleansoft.com"
  ;; connection timed out; no servers could be reached

where I've blunked out my client's DNS host address. So what does this 
mean? I thought -C meant to try to find the authoritative nameserver.

Here is my zone file for cleansoft.com. Note, this setup has been working 
for a couple of months until Friday morning, and I haven't changed anything 
related to BIND that I am aware of, though there may have been a system 
reboot in there that I don't know about. I checked my record with my domain 
registrar, and it shows ns1.cleansoft.com 198.49.126.122 as primary 
nameserver for this domain.

cleansoft.com.  IN SOA  ns1.cleansoft.com. postmaster.cleansoft.com. (
                                 6       ; Serial
                                 10800   ; Refresh after 3 hours
                                 3600    ; Retry after 1 hour
                                 604800  ; Expire after 1 week
                                 86400   ; Minimum TTL of 1 day
)

cleansoft.com.  IN NS   ns1.cleansoft.com.
cleansoft.com.  IN NS   ns2.cleansoft.com.

;
; Host addresses
;

localhost.cleansoft.com.        IN A    127.0.0.1
www.cleansoft.com.              IN A    198.49.126.122
cleansoft.com.                  IN A    198.49.126.122
mail.cleansoft.com.             IN A    198.49.126.122
ns1.cleansoft.com.              IN A    198.49.126.122
ns2.cleansoft.com.              IN A    198.49.126.122
cleansoft.com.                  IN MX   0 cleansoft.com.



Michael Deck
Cleanroom Software Engineering, Inc.