Domain information and DNS

Domain information and DNS

When we need information about a domain, for example, google.com, we can use the “nslookup” command on Linux, windows, and Mac_os

 

 

 

By executing the command

nslookup google.com

we get the following information even if not all “machines” provide the exact same answer (then we’ll see why it happens)

Server: 192.168.1.254
Address: 192.168.1.254 # 53

Non-authoritative answer:
Name: google.com
Address: 216.58.205.46

What the meaning of all those lines?
Where is this information?

Server: 192.168.1.254

192.168.1.254 is the address of the server to which our computer asks for information about the domain.
This IP address provides a service to respond to this type of queries (in a subsequent article we will see how)

Usually, if we have a home connection that is the IP address of our “router” (or what some people call “modem” inappropriately)

Address: 192.168.1.254 # 53

The IP address 192.168.1.254 of the “DNS” service which gives back the information via the port 53 “

Non-authoritative answer:

This means that our DNS on 192.168.1.254 (at the door) gives us an answer but non-authoritative, which is good anyway 🙂 the non-authoritative response is

Name: google.com
Address: 216.58.205.46

This answer should not require clarification.
All computers on the Internet can be reached not by their name but by their IP then the computer google.com and on ‘IP 216.58.205.46.

Now let’s take a small step forward and add a parameter to the nslookup command and launch

nslookup -q = ns google.com

-q = stands for query
ns stands for name server

the answer is now

Server: 188 165 200 114
Address: 188 165 200 114 # 53

Non-authoritative answer:
google.com nameserver = ns4.google.com.
google.com nameserver = ns3.google.com.
google.com nameserver = ns2.google.com.
google.com nameserver = ns1.google.com.

Authoritative answers can be found from:
ns1.google.com internet address = 216.239.32.10
ns1.google.com has AAAA address 2001: 4860: 4802: 32 :: a
ns2.google.com internet address = 216.239.34.10
ns2.google.com has AAAA address 2001: 4860: 4802: 34 :: a
ns3.google.com internet address = 216.239.36.10
ns3.google.com has AAAA address 2001: 4860: 4802: 36 :: a
ns4.google.com internet address = 216.239.38.10
ns4.google.com has AAAA address 2001: 4860: 4802: 38 :: a

now the thing is complicated apparently but it makes a fundamental thing clearer.

If you query the domain via an authoritative dsn :

You’ll get back :
Server: ns4.google.com
Address: 216.239.38.10#53
Name: google.com
Address: 216.58.205.46
The message “Non-authoritative answer:”  it’s not longer showed since ns4.google.com is an authoritative server for google.com

“Where Authoritative answers can be found from:”

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