[c-nsp] DNS Tool

[Ted Mittelstaedt]

Without having a more detailed explanation of what browsing
problems your having, it's difficult to give any more specific
advice, but here goes:

1) browsers cache DNS lookups, so if your having repetitive
lookups fail off the same browser session, it's not actually a
DNS problem even though it might seem like one.

2) client operating systems also cache DNS lookups so if
your having repetitive lookups fail off multiple browser sessions
it's not actually a DNS problem even though it might seem like one.

3) if lookups work fine with nslookup but appear to fail in the
browser it's not actually a DNS problem

4) If you override your client OS DNS server IP addresses with
your ISP's DNS server IP addresses and you have lookup problems
it's not actually a DNS problem.

I think you probably are starting to get the picture here - many
things that people -think- are DNS problems actually aren't.  As
long as your being coy about what the exact problem is, your not
going to get much useful advice from us.  There's no need to be
embarassed, all of us have gone through these kinds of problems
before, often of our own making.

Practially all "DNS problems" I've ever troubleshot turned out
to be layer-2 problems, not DNS problems.

Just a thought.

Ted

Mohammad Khalil wrote:
> We are facing some browsing problems , so we want to make sure that our DNS servers are resolving well using tools other than nslookup
> 
>> Date: Wed, 8 Apr 2009 14:42:50 -0700
>> From: walter.keen at rainierconnect.net
>> To: eng_mssk at hotmail.com
>> CC: cisco-nsp at puck.nether.net
>> Subject: Re: [c-nsp] DNS Tool
>>
>> Could you elaborate a little?
>>
>> We use Nagios to monitor other things, and use a DNS check plugin that
>> simply does a dns query and reports if it successfully got an answer.  I
>> think there are other ones that will compare the answer to a known good
>> answer you supply (wouldn't work well with something like Google.com or
>> yahoo.com that does a lot of round robin entries)
>>
>> Mohammad Khalil wrote:
>>> Hey all
>>> is there any tool that can monitor the DNS behavior ??
>>> for example , the resolving process and if there are any errors ??
>>>
>>> Thanks
>>>
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