How to Query DNS Records Using nslookup with a Specific DNS Server

The nslookup command is a powerful network administration tool used for querying the Domain Name System (DNS) to obtain domain name or IP address mapping, DNS record types, and other DNS information. By default, when you use nslookup, it utilizes your system’s configured DNS resolver, which typically points to your Internet Service Provider’s (ISP) DNS servers. However, there are scenarios where you might need to query DNS records using a specific DNS server. This article will guide you on how to effectively use nslookup to query DNS records from a DNS server of your choice.

To direct nslookup to use a specific DNS server, you simply need to append the IP address or hostname of the desired DNS server at the end of your nslookup command.

For example, to query the DNS records for isc.org using Google’s Public DNS server (at IP address 8.8.8.8), you would use the following command:

nslookup isc.org 8.8.8.8

In this command, nslookup will bypass the default DNS resolver and directly contact the DNS server at 8.8.8.8 to fetch the DNS records for isc.org. This is incredibly useful for troubleshooting DNS resolution issues or verifying DNS propagation across different servers.

The general syntax for the nslookup command when specifying a DNS server is:

nslookup [-option ...] domain-name [dns-server]

Understanding the parameters in nslookup for specifying a DNS server.

Accessing nslookup Documentation from the Command Line

If you need a quick reminder about the syntax and options available in nslookup, you can easily access the documentation directly from your command line.

On Windows systems, simply type the following command and press Enter:

nslookup /?

This will display a concise help message outlining the basic usage and options for nslookup on Windows.

For users on Linux or macOS, the manual page (man) command is the standard way to access comprehensive documentation for command-line tools. To view the nslookup manual, type:

man nslookup

This command will open the full manual page for nslookup, providing detailed information about all its features, options, and usage examples.

Specifying a Non-Standard Port Number

DNS typically operates on port 53. However, in certain situations, a DNS server might be configured to listen on a different port. If you need to query a DNS server that is using a non-standard port, you can instruct nslookup to use that specific port using the -port option.

For instance, if a DNS server is running on port 42, you can specify this port in your nslookup command like this:

nslookup -port=42 isc.org 8.8.8.8

This command will ensure that nslookup attempts to connect to the DNS server at 8.8.8.8 on port 42 instead of the default port 53.

Setting a DNS Server in nslookup Interactive Mode

nslookup also offers an interactive mode, which is useful for performing multiple DNS queries in a session without retyping the nslookup command repeatedly. To enter interactive mode, simply type nslookup in your command line and press Enter, without specifying a domain name.

Once in interactive mode, you can set a specific DNS server to be used for all subsequent queries within that session. To switch to Google’s Public DNS servers (8.8.8.8), use the server command followed by the DNS server’s IP address:

nslookup
Default Server:  UnKnown
Address:  fe80::21c:42ff:fe00:18

> server 8.8.8.8
Default Server:  dns.google
Address:  8.8.8.8
> set port=53

After executing the server command, all subsequent DNS lookups within the interactive nslookup session will be directed to the specified DNS server (in this case, 8.8.8.8). You can also use lserver instead of server. The lserver command forces nslookup to use your initially configured local DNS resolver to find the address of the new DNS server, which can be helpful in specific network configurations. If you are using the IP address of the DNS server, there is no practical difference between server and lserver.

Querying DNS Records Across Multiple Servers

While nslookup is excellent for querying individual DNS servers, it doesn’t natively support querying multiple DNS servers simultaneously in a single command. To check DNS records across several servers using nslookup, you would need to execute the command multiple times, each time specifying a different DNS server.

For a more efficient way to check DNS propagation across a range of global and regional DNS servers, consider utilizing a dedicated online DNS checker. These tools are designed to perform DNS lookups against numerous servers concurrently, providing a comprehensive view of DNS record propagation and consistency.

By mastering the techniques outlined in this guide, you can effectively leverage nslookup to query DNS records from specific DNS servers for network troubleshooting, DNS verification, and deeper insights into DNS resolution processes.