What is Nslookup?
First, let’s talk about what Nslookup is – it is a small but very powerful network administration command-line software. It has a simple interface, but it is useful. The Nslookup command is available on many of the popular computer operating systems like Windows, ReactOS, different, and Linux distros. You can use it to perform DNS queries and receive: domain names or IP addresses, or any other specific DNS Records.
There are Nslookup online tools too. You can access such a site full of online network tools and search for the option for nslookup. You can define your query for a specific DNS record, to identify the domain, the port in use, and timeout in seconds. For better security, we recommend you to use the software on your computer.
If you want high speed, you must use Anycast DNS services! Check this article about Anycast DNS!
Here are the 10 most used Nslookup commands that will help you to understand better your domain’s management:
1. How to find the A record of а domain.
You can use this command to see how many A records are there and see the IP Addresses of each one.
$ nslookup example.com
2. How to check the NS records of a domain.
By checking the NS records, you can see which is the authoritative server for a specific domain.
$nslookup -type=ns example.com
3. How to query the SOA record of a domain.
With this one, you can see the start of authority and get information about the zone.
$nslookup -type=soa example.com
4. How to find the MX records responsible for the email exchange.
Here we are checking the MX records of the mail servers. You can see if all the mail servers are working well.
$ nslookup -query=mx example.com
5. How to find all of the available DNS records of a domain.
This lookup has a large scope. Here we want to see all the available DNS records. After seeing all of them, we can do specific lookups for different types of DNS records.
$ nslookup -type=any example.com
6. How to check the using of a specific DNS Server.
Apart from checking DNS records, you can use the Nslookup to review a particular DNS server and how it works. You can check if it is active or if it responds on time.
$ nslookup example.com ns1.nsexample.com
7. How to check the Reverse DNS Lookup.
Many times you check the A records to see the IPs of a domain, but sometimes you need to verify if an IP address is related to a specific domain. For that purpose, we need a reverse DNS lookup.
$ nslookup 10.20.30.40
8. Nslookup command to change the port number for the connection.
You can check the connection through different ports. This can help you to see if there are open ports that you don’t use. Later you can close them for security reasons.
$ nslookup -port=56 example.com
9.How to change the timeout interval for a reply.
You can manually choose the timeout time in seconds. You can increase it to give more time for the server to respond. You can also shorter it to see which servers can respond quicker.
$ nslookup -timeout=20 example.com
10. How to enable debug mode.
Debug mode provides important and detailed information both for the question and for the received answer.
$ nslookup -debug example.com
Nslookup is one of the popular command-line software for DNS probing. You can use it to monitor your network and spot problematic areas. If you are interested in similar tools, you can see Ping, Traceroute, Dig, and Host too. You can use them together or find one that covers all of your diagnostic needs.
Need more details what is nslookup? Check the nslookup page on wikipedia.
Authoritative answer – This is the answer that originates from the DNS Server which has the information about the zone file.
Non-authoritative answer – When a nameserver is not in the list for the domain you did a lookup on.
Different port – By default, the DNS servers use port 53.