nslookup — Query DNS records

Linux / Network and Firewall / nslookup.html

Resolves names to addresses and addresses to names, and shows which DNS server answered.

Basic Information

What is this command?

nslookup asks a DNS server how a name and an address map to each other.

You can query a specific server instead of the default one, which helps compare answers.

What problems does it solve?

• Check which address a domain resolves to.
• Inspect the answer of one specific DNS server.
• Look up record types such as MX, NS or TXT.
• Tell whether a resolution failure is local or server-side.

Key features

Default lookup

Passing a name or address queries the default resolver.

• When to use: When you want the configured resolver's answer.
• What you get: The name-to-address mapping is printed.
• Limitations: Cached answers may differ from the authoritative server.

Query a specific server

A second argument selects the DNS server to ask.

• When to use: When comparing answers between servers.
• What you get: Only the chosen server's answer appears.
• Limitations: No answer arrives if that server is unreachable.

Record type queries

Use set type= to ask for MX, NS, TXT and other records.

• When to use: When checking mail servers or ownership records.
• What you get: Records of that type are listed.
• Limitations: Some types answer correctly only from the authoritative server.

Installation and usage

Check whether it is installed

nslookup -version

sudo apt install dnsutils

Real-world examples

Resolve a name

Look up the A record of a domain.

nslookup example.com

Choose a server

Ask a public resolver directly.

nslookup example.com 1.1.1.1

MX record

Inspect mail exchanger records.

nslookup -type=MX example.com