Diagnostic Tools for DNS
1. dig
mail2# dig

; <<>> DiG 8.3 <<>>
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 4
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUERY SECTION:
;; ., type = NS, class = IN

;; Total query time: 1 msec
;; FROM: mail2 to SERVER: default –192.168.0.1
;; WHEN: Fri Oct 24 15:53:37 2003
;; MSG SIZE sent: 17 rcvd: 17
2. host
host mail2
mail2.com has address 192.168.0.1
Usage: host [-adlrwv] [-t querytype] [-c class] host [server]
-a is equivalent to '-v -t *'
-c class to look for non-Internet data
-d to turn on debugging output
-l to turn on 'list mode'
-r to disable recursive processing
-s recursively chase signature found in answers
-t querytype to look for a specific type of information
-v for verbose output
-w to wait forever until reply
3 .nslookup
nslookup
Default Server: mail2.com
Address: 192.168.0.1
> www
Server: mail2.com
Address: 192.168.0.1

Non-authoritative answer:
Name: mail2.com
Address: 192.168.0.1
Aliases: www. mail2.com

Administrative tools
Named-checkconf [-t directory] [filename]
Named-checkzone
Rndc