To troubleshoot DNS use the dig and host commands.
ubuntu:~$ dig www.ccie23050.com @4.2.2.2
; <<>> DiG 9.7.1-P2 <<>> www.ccie23050.com @4.2.2.2
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45168 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;www.ccie23050.com. IN A ;; ANSWER SECTION: www.ccie23050.com. 3600 IN CNAME ccie23050.com. ccie23050.com. 3600 IN A 33.67.33.89 ;; Query time: 128 msec ;; SERVER: 4.2.2.2#53(4.2.2.2) ;; WHEN: Mon Mar 7 10:47:00 2011 ;; MSG SIZE rcvd: 65 To troubleshoot a reverse lookup use the -x option. ubuntu:~$ dig -x 209.191.122.70 ; <<>> DiG 9.7.1-P2 <<>> -x 209.191.122.70
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39053 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;70.122.191.209.in-addr.arpa. IN PTR ;; ANSWER SECTION: 70.122.191.209.in-addr.arpa. 1186 IN PTR ir1.fp.vip.mud.yahoo.com. ;; Query time: 0 msec ;; SERVER: 4.2.2.2#53(4.2.2.2) ;; WHEN: Mon Mar 7 11:22:00 2011 ;; MSG SIZE rcvd: 83 ubuntu:~$ host www.ccie23050.com www.ccie23050.com is an alias for ccie23050.com. ccie23050.com has address 33.67.33.89 ccie23050.com mail is handled by 0 smtp.secureserver.net. ccie23050.com mail is handled by 10 mailstore1.secureserver.net.