Domain Information Groper

From Wikipedia, the free encyclopedia

Domain Information Groper (abbreviated dig, or sometimes DiG) is a network tool, like nslookup, that queries DNS name servers. It can be used to simulate a DNS resolver or a name server. DiG can be used for network troubleshooting and for educational purposes.

Here's an example of using DiG:

$ dig ce.sharif.edu
; <<>> DiG 9.2.4 <<>> ce.sharif.edu
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23567
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;ce.sharif.edu.                 IN      A

;; ANSWER SECTION:
ce.sharif.edu.          864000  IN      A       81.31.164.3

;; AUTHORITY SECTION:
ce.sharif.edu.          864000  IN      NS      netserver.ce.sharif.edu.

;; ADDITIONAL SECTION:
netserver.ce.sharif.edu. 864000 IN      A       81.31.164.2

;; Query time: 1 msec
;; SERVER: 81.31.164.2#53(81.31.164.2)
;; WHEN: Wed Nov  1 17:02:16 2006
;; MSG SIZE  rcvd: 87

Another example, using an MX record:

$ dig MX yahoo.com

; <<>> DiG 9.3.2 <<>> MX yahoo.com
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50065
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 7, ADDITIONAL: 7

;; QUESTION SECTION:
;yahoo.com.                     IN      MX

;; ANSWER SECTION:
yahoo.com.              3290    IN      MX      1 f.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 g.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 a.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 b.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 c.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 d.mx.mail.yahoo.com.
yahoo.com.              3290    IN      MX      1 e.mx.mail.yahoo.com.

;; AUTHORITY SECTION:
yahoo.com.              157925  IN      NS      ns2.yahoo.com.
yahoo.com.              157925  IN      NS      ns3.yahoo.com.
yahoo.com.              157925  IN      NS      ns4.yahoo.com.
yahoo.com.              157925  IN      NS      ns5.yahoo.com.
yahoo.com.              157925  IN      NS      ns8.yahoo.com.
yahoo.com.              157925  IN      NS      ns9.yahoo.com.
yahoo.com.              157925  IN      NS      ns1.yahoo.com.

;; ADDITIONAL SECTION:
ns1.yahoo.com.          150856  IN      A       66.218.71.63
ns2.yahoo.com.          47503   IN      A       68.142.255.16
ns3.yahoo.com.          157925  IN      A       217.12.4.104
ns4.yahoo.com.          47503   IN      A       68.142.196.63
ns5.yahoo.com.          150856  IN      A       216.109.116.17
ns8.yahoo.com.          53868   IN      A       202.165.104.22
ns9.yahoo.com.          53868   IN      A       202.160.176.146

;; Query time: 4 msec
;; SERVER: 194.105.19.22#53(194.105.19.22)
;; WHEN: Wed May  9 20:10:48 2007
;; MSG SIZE  rcvd: 399

[edit] Types of records

A record maps a host to an IPv4 address.
AAAA record maps a host to an IPv6 address. (The use of four A's is because an IPv6 address is four times as long as an IPv4 address.)
CNAME record maps a host to its canonical name.
LOC record provides a geographical location for a host. Rarely used.
MX record comes from a mail exchange, and indicates where mail for a specific domain should be delivered.
NS record indicates the name server that handles DNS queries for a domain.
PTR record (short for “pointer”) maps an IP address to a hostname.
SOA record specifies the DNS server providing authoritative information about an Internet domain.
SRV record advertises services available on a host. It is a generalization of the MX record, used for load balancing.
TXT records are used to include arbitrary text to a DNS record.