DNS lookup of GTLD servers using dig

I ran the following command on linux

>> dig .

I got the following response

;; AUTHORITY SECTION:
.           281 IN  SOA A.ROOT-SERVERS.NET. NSTLD.VERISIGN-GRS.COM.     2010032400 1800 900 604800 86400

why does the response not contain the IP address of the root server?
what do the numbers at the end of the reply mean. one of them is probably (definitely) the date.
why does it report 2 root servers a.root and nstld.verisign?
when i send the following queries

dig com.

;; AUTHORITY SECTION:com. 51 IN SOA a.gtld-servers.net. nstld.verisign-grs.com. 1269425283 1800 900 604800 86400

again i do not get the ip addresses. when i query for the gtld server specified i can get the ip address. why is the response of dig net. same as that of dig com. except that instead of 51 we have 19 in the response.

Rohit Banga

Posted 2010-03-24T10:24:40.490

Reputation: 1 814

Anything in .digrc? Do you get the same result if you run /usr/bin/dig? – Fred – 2010-03-24T13:17:33.190

no .digrc file found – Rohit Banga – 2010-03-24T19:38:27.107

/usr/bin/dig . gives no response. but for others same response. – Rohit Banga – 2010-03-24T19:38:59.027

i am expecting additional records containing ip addresses. – Rohit Banga – 2010-03-24T19:40:00.397

Answers

"why does the response not contain the IP address of the root server?"

Because you did not ask for it. dig NS . will give you the names of the root name serverS, together with the IP addresses.

"what do the numbers at the end of the reply mean. one of them is probably (definitely) the date."

No, it is the serial number of the root zone, which may be encoded as a date but not always (compare the root with .com or .fr). The other numbers are useful only for the secondary name servers and are described in RFC 1035, section 3.3.13 (note the last number, Minimum, acquired a new meaning since RFC 1035 was issued).

"why does it report 2 root servers a.root and nstld.verisign?"

No, it does not. NSTLD.VERISIGN-GRS.COM is the email address of the zone manager (the @ has a special signification in traditional zone files, so it is replaced by the first dot).

"why is the response of dig net. same as that of dig com. except that instead of 51 we have 19 in the response."

This is the TTL (Time To Live) and it decreases at each query. Try dig com several times.

bortzmeyer

Posted 2010-03-24T10:24:40.490

Reputation: 1 083