DNS nslookup debugging

article #103, updated 3494 days ago

This one comes from the excellent David Childers.

When you start up nslookup in a command prompt, there’s a way to get some very good additional information.

C:\Documents and Settings\davidc>nslookup -d2
------------
SendRequest(), len 41
HEADER:
opcode = QUERY, id = 1, rcode = NOERROR
header flags:  query, want recursion
questions = 1,  answers = 0,  authority records = 0,  additional = 0

QUESTIONS:
3.1.16.172.in-addr.arpa, type = PTR, class = IN

------------
------------
Got answer (78 bytes):
HEADER:
opcode = QUERY, id = 1, rcode = NOERROR
header flags:  response, auth. answer, want recursion, recursion avail.
questions = 1,  answers = 1,  authority records = 0,  additional = 0

QUESTIONS:
3.1.16.172.in-addr.arpa, type = PTR, class = IN
ANSWERS:
->  3.1.16.172.in-addr.arpa
type = PTR, class = IN, dlen = 25
name = ***-***.********.local
ttl = 1200 (20 mins)

------------
Default Server:  ***-***.********.local
Address:  172.16.1.3

--------------------------------------------

As you can see, by using the command nslookup -d2, the entirety of the conversation that nslookup is having with the DNS server is displayed.

If you believe that nslookup has locked up or died, you will be able to see the timeouts occurring as it waits for response from the DNS server.

I hope that helps!

:-)

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