nslookup on ukko

The UNIX nslookup program can be used to determine a variety of information about machines and domains in the internet. It uses the Domain Name System (DNS) protocol. Its most important use is translating host names to Internet Protocol (IP) addresses. IP addresses are required for routing data through the internet.

For security reasons, most machines and domains will not respond to all types of queries made by nslookup. Most will respond to the query types described in the following sections. In these examples everything typed by the the user is shown with a light blue background.

Finding the Address of a Machine

Here is an example using nslookup to find the address of bulldog.d.umn.edu. The first two lines give the local server from which the query originates. They are the same in all of the examples below. The answer to the query is in the following lines.

ukko 1% nslookup -type=a bulldog.d.umn.edu
Server:		131.212.32.32
Address:	131.212.32.32#53

Name:	bulldog.d.umn.edu
Address: 131.212.109.98

Finding the Mail Exchanger for a Domain

Here is an example using nslookup to find the mail exchanger for a network domain. A non-authoritative answer means the local DNS server is returning information that it had cached from earlier queries.

There are two kinds of IP addresses in the section that describes where you can get authoritative information:

"internet address" refers to IP version 4 (IPv4) addresses. These addresses are 32 bits.
"AAAA address" refers to IP version 6 (IPv6) addresses. These addresses are 128 bits.

ukko 2% nslookup -type=mx tc.umn.edu
Server:		131.212.32.32
Address:	131.212.32.32#53

Non-authoritative answer:
tc.umn.edu	mail exchanger = 10 mhub-m.tc.umn.edu.
tc.umn.edu	mail exchanger = 10 mhub-w.tc.umn.edu.
tc.umn.edu	mail exchanger = 10 mhub-a.tc.umn.edu.

Authoritative answers can be found from:
umn.edu	nameserver = ns-auth-2.umn.edu.
umn.edu	nameserver = ns-auth-1.umn.edu.
umn.edu	nameserver = ns-auth-remote-1.umn.edu.
ns-auth-1.umn.edu	internet address = 128.101.101.1
ns-auth-1.umn.edu	has AAAA address 2001:468:1910:4801::2
ns-auth-2.umn.edu	internet address = 128.101.101.9
ns-auth-2.umn.edu	has AAAA address 2001:468:1910:4802::2
ns-auth-remote-1.umn.edu	internet address = 140.142.16.240

Finding the Name Server for a Domain

Here are examples using nslookup to find the name server for a domain. A domain is an administrative unit for a group of machines. The administrative units form a hierarchy.

The full hostname for a machine encodes the domains it belongs to. For example

The machine ukko.d.umn.edu is directly in the d.umn.edu domain, which is administered by UMD.
The d.umn.edu domain is a subdomain of umn.edu, which is administered by the University of Minnesota.
The umn.edu domain is a subdomain of edu, which is administered by EDUCAUSE.

ukko 3% nslookup -type=ns mit.edu
Server:		131.212.32.32
Address:	131.212.32.32#53

Non-authoritative answer:
mit.edu	nameserver = W20NS.mit.edu.
mit.edu	nameserver = bitsy.mit.edu.
mit.edu	nameserver = STRAWB.mit.edu.

Authoritative answers can be found from:
bitsy.mit.edu	internet address = 18.72.0.3
W20NS.mit.edu	internet address = 18.70.0.160
STRAWB.mit.edu	internet address = 18.71.0.151

ukko 4% nslookup -type=ns edu
Server:		131.212.32.32
Address:	131.212.32.32#53

Non-authoritative answer:
edu	nameserver = l.edu-servers.net.
edu	nameserver = c.edu-servers.net.
edu	nameserver = a.edu-servers.net.
edu	nameserver = g.edu-servers.net.
edu	nameserver = f.edu-servers.net.
edu	nameserver = d.edu-servers.net.

Authoritative answers can be found from:
a.edu-servers.net	internet address = 192.5.6.30
c.edu-servers.net	internet address = 192.26.92.30
d.edu-servers.net	internet address = 192.31.80.30
f.edu-servers.net	internet address = 192.35.51.30
g.edu-servers.net	internet address = 192.42.93.30
g.edu-servers.net	has AAAA address 2001:503:cc2c::2:36
l.edu-servers.net	internet address = 192.41.162.30