Network troubleshooting, any experts?

[Jeff Vian]

Elam Daly wrote:

> gforte wrote:
>
>> With all (un)due respect, your ISP is probably full of crap.  Your 
>> tcpdumps
>> indicate that your UDP connections to the DNS servers are getting 
>> through,
>> at the least.  That's why you're able to resolve hostnames.  The fact 
>> that
>> your TCP syns never get responded to suggest that they are being blocked
>> someplace.  If the server is not running any firewall as you say, 
>> then the
>> only other logical place is at the border router.
>>
>> -g
>
>
>
> Does DNS resolve names through UDP?  Would that explain why I can't 
> telnet
> to port 53 on the DNS servers,yet still get name resolutions?  Am I 
> wrong conceptually
> on how DNS works?
> Thanks
> Elam
>
YES, and YES
DNS service uses UDP,
Telnet is TCP

However, there still appears to be a TCP block.  If you look at 
/etc/services you see port 53 is defined as domain for both TCP and UDP.