tips on debugging DNS

[Kimi Ostro]

More info:

Both 192.0.2.212 & 192.0.2.213 are the internal authoratative only
nameservers listed in resolv.conf & handed out by DHCP, and
192.0.2.216 is the caching recursive name server.

nslookup
> www.google.com.
Server:         192.0.2.212
Address:        192.0.2.212#53

** server can't find www.google.com: REFUSED
>
tcpdump:
ethertype IPv4 (0x0800), length 74: 192.0.2.150.50947 >
192.0.2.212.53:  65432+ A? www.google.com. (32)
ethertype IPv4 (0x0800), length 74: 192.0.2.212.53 >
192.0.2.150.50947:  65432 Refused- 0/0/0 (32)

nslookup
> www.google.com.
Server:         192.0.2.213
Address:        192.0.2.213#53

** server can't find www.google.com: REFUSED
>
tcpdump:
ethertype IPv4 (0x0800), length 74: 192.0.2.150.50947 >
192.0.2.213.53:  65432+ A? www.google.com. (32)
ethertype IPv4 (0x0800), length 74: 192.0.2.213.53 >
192.0.2.150.50947:  65432 Refused- 0/0/0 (32)

nslookup
> server 192.0.2.216
Default server: 10.8.8.216
Address: 192.0.2.216#53
> www.google.co.uk.
;; connection timed out; no servers could be reached
tcpdump:
ethertype IPv4 (0x0800), length 74: 192.0.2.150.54209 >
192.0.2.216.53:  59525+ A? www.google.com. (32)
ethertype IPv4 (0x0800), length 74: 192.0.2.150.54209 >
192.0.2.216.53:  59525+ A? www.google.com. (32)
ethertype IPv4 (0x0800), length 74: 192.0.2.150.54209 >
192.0.2.216.53:  59525+ A? www.google.com. (32)
ethertype IPv4 (0x0800), length 74: 192.0.2.216.53 >
192.0.2.150.54209:  59525 ServFail 0/0/0 (32)

-- 
Kimi