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By Root 3066 0

with BIND. dig, the domain information groper, was originally written by Steve Hotz and was rewritten for BIND 9 by Michael Sawyer. It is shipped with BIND as well. host, by Eric Wassenaar, is another open source tool; it features user-friendly output and functions to check the syntax of your zone files. We discuss each of these tools but prefer dig over nslookup; we like host, too. You might sometimes get different results from these tools because of the different resolver libraries that they use; dig and host use BIND’s resolver, and nslookup has its own.

nslookup and dig are included in the BIND release.

nslookup is a user-level command that queries the DNS database. It expects fully qualified names ending in a dot and appends the default domain if you forget the dot. For local names, this behavior is often what you want. Table 16.16 gives a short list of nslookup commands.

Table 16.16 Commands understood by nslookup

a. any is a good value that means “all record types.”

dig provides the same rough functionality as nslookup, but it has more sensible defaults, provides more information, and has a nicer user interface (especially when compared to older versions of nslookup).

For example, to ask for anchor’s MX records, use

% dig anchor.cs.colorado.edu. mx

The command

% dig @ns1.berkeley.edu vangogh.berkeley.edu. any

obtains vangogh’s complete records from a berkeley.edu server, and

% dig -x 128.32.33.5

performs a reverse query for vangogh. Here is a complete example that uses both nslookup and dig to query for the same data:

% nslookup

Default Server: bb.rc.vix.com

Address: 204.152.187.11

> set type=any

> amazon.com.

Server: bb.rc.vix.com

Address: 204.152.187.11

Non-authoritative answer:

amazon.com nameserver = AUTH00.NS.UU.NET

amazon.com nameserver = NS2.PNAP.NET

amazon.com nameserver = NS1.PNAP.NET

amazon.com nameserver = NS-1.amazon.com

amazon.com preference = 10, mail exchanger = service-4.amazon.com

amazon.com preference = 10, mail exchanger = service-5.amazon.com

amazon.com internet address = 208.216.182.15

Authoritative answers can be found from:

amazon.com nameserver = AUTH00.NS.UU.NET

amazon.com nameserver = NS2.PNAP.NET

amazon.com nameserver = NS1.PNAP.NET

amazon.com nameserver = NS-1.amazon.com

AUTH00.NS.UU.NET internet address = 198.6.1.65

NS2.PNAP.NET internet address = 206.253.194.97

NS1.PNAP.NET internet address = 206.253.194.65

NS-1.amazon.com internet address = 209.191.164.20

service-4.amazon.com internet address = 209.191.164.50

service-5.amazon.com internet address = 209.191.164.51

nslookup returns four NS records, two MX records, and an A record. It also provides the IP addresses of the name servers and MX hosts.

% dig amazon.com. any

; <<>> DiG 8.3 <<>> amazon.com any

;; res options: init recurs defnam dnsrch

;; got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4

;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 4, ADDITIONAL: 6

;; QUERY SECTION:

;; amazon.com, type = ANY, class = IN

;; ANSWER SECTION:

amazon.com. 1h27m11s IN NS AUTH00.NS.UU.NET.

amazon.com. 1h27m11s IN NS NS2.PNAP.NET.

amazon.com. 1h27m11s IN NS NS1.PNAP.NET.

amazon.com. 1h27m11s IN NS NS-1.amazon.com.

amazon.com. 59m22s IN MX 10 service-4.amazon.com.

amazon.com. 59m22s IN MX 10 service-5.amazon.com.

amazon.com. 1h59m29s IN A 208.216.182.15

;; AUTHORITY SECTION:

amazon.com. 1h27m11s IN NS AUTH00.NS.UU.NET.

amazon.com. 1h27m11s IN NS NS2.PNAP.NET.

amazon.com. 1h27m11s IN NS NS1.PNAP.NET.

amazon.com. 1h27m11s IN NS NS-1.amazon.com.

;; ADDITIONAL SECTION:

AUTH00.NS.UU.NET. 13h11m20s IN A 198.6.1.65

NS2.PNAP.NET. 20h51m44s IN A 206.253.194.97

NS1.PNAP.NET. 20h51m44s IN A 206.253.194.65

NS-1.amazon.com. 59m22s IN A 209.191.164.20

service-4.amazon.com. 59m22s IN A 209.191.164.50

service-5.amazon.com. 59m22s IN A 209.191.164.51

;; Total query time: 7 msec

;; FROM: bb.rc.vix.com to SERVER: default -- 204.152.187.11

;; WHEN: Sun Jul 2 12:45:59 2000

;; MSG SIZE sent: 28 rcvd: 338

dig is verbose. Its output includes not only