8 Linux Nslookup Commands to Troubleshoot DNS (Domain Name Server)


nslookup is a command-line administrative tool for testing and troubleshooting DNS servers (Domain Name Server). It is used to query specific DNS resource records (RR) as well. Most operating systems come with a built-in nslookup feature.

This article demonstrates the widely used nslookup command in detail. Nslookup can be run in two modes: Interactive and Non-Interactive.

The Interactive mode is used to query DNS-Server about various domains and hosts. Non-Interactive mode is used to query about information of a domain or host.

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1. Find out “A” record (IP address) of Domain

# nslookup yahoo.com

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
Name:   yahoo.com
Address: 72.30.38.140
Name:   yahoo.com
Address: 98.139.183.24
Name:   yahoo.com
Address: 209.191.122.70

Above command query domain www.yahoo.com with 4.2.2.2 public DNS server and below section shows Non-authoritative answer: displays A record of www.yahoo.com

2. Find out Reverse Domain Lookup

# nslookup 209.191.122.70

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
70.122.191.209.in-addr.arpa     name = ir1.fp.vip.mud.yahoo.com.

Authoritative answers can be found from:

3. Find out specific Domain Lookup.

# nslookup ir1.fp.vip.mud.yahoo.com.

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
Name:   ir1.fp.vip.mud.yahoo.com
Address: 209.191.122.70

4. To Query MX (Mail Exchange) record.

# nslookup -query=mx www.yahoo.com

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
www.yahoo.com   canonical name = fd-fp3.wg1.b.yahoo.com.
fd-fp3.wg1.b.yahoo.com  canonical name = ds-fp3.wg1.b.yahoo.com.
ds-fp3.wg1.b.yahoo.com  canonical name = ds-any-fp3-lfb.wa1.b.yahoo.com.
ds-any-fp3-lfb.wa1.b.yahoo.com  canonical name = ds-any-fp3-real.wa1.b.yahoo.com.

Authoritative answers can be found from:
wa1.b.yahoo.com
        origin = yf1.yahoo.com
        mail addr = hostmaster.yahoo-inc.com
        serial = 1344827307
        refresh = 30
        retry = 30
        expire = 86400
        minimum = 1800

MX record is being used to map a domain name to a list of mail exchange servers for that domain. So that it tells that whatever mail received/sent to @yahoo.com will be routed to the mail server.

5. To query NS(Name Server) record.

# nslookup -query=ns www.yahoo.com

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
www.yahoo.com   canonical name = fd-fp3.wg1.b.yahoo.com.
fd-fp3.wg1.b.yahoo.com  canonical name = ds-fp3.wg1.b.yahoo.com.
ds-fp3.wg1.b.yahoo.com  canonical name = ds-any-fp3-lfb.wa1.b.yahoo.com.
ds-any-fp3-lfb.wa1.b.yahoo.com  canonical name = ds-any-fp3-real.wa1.b.yahoo.com.

Authoritative answers can be found from:
wa1.b.yahoo.com
        origin = yf1.yahoo.com
        mail addr = hostmaster.yahoo-inc.com
        serial = 1344827782
        refresh = 30
        retry = 30
        expire = 86400
        minimum = 1800

6. To query SOA (Start of Authority) record.

# nslookup -type=soa www.yahoo.com

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
www.yahoo.com   canonical name = fd-fp3.wg1.b.yahoo.com.
fd-fp3.wg1.b.yahoo.com  canonical name = ds-fp3.wg1.b.yahoo.com.
ds-fp3.wg1.b.yahoo.com  canonical name = ds-any-fp3-lfb.wa1.b.yahoo.com.
ds-any-fp3-lfb.wa1.b.yahoo.com  canonical name = ds-any-fp3-real.wa1.b.yahoo.com.

Authoritative answers can be found from:
wa1.b.yahoo.com
        origin = yf1.yahoo.com
        mail addr = hostmaster.yahoo-inc.com
        serial = 1344827965
        refresh = 30
        retry = 30
        expire = 86400
        minimum = 1800

7. To query all Available DNS records.

# nslookup -query=any yahoo.com

Server:         4.2.2.2
Address:        4.2.2.2#53

Non-authoritative answer:
yahoo.com
        origin = ns1.yahoo.com
        mail addr = hostmaster.yahoo-inc.com
        serial = 2012081016
        refresh = 3600
        retry = 300
        expire = 1814400
        minimum = 600
Name:   yahoo.com
Address: 98.139.183.24
Name:   yahoo.com
Address: 209.191.122.70
Name:   yahoo.com
Address: 72.30.38.140
yahoo.com       mail exchanger = 1 mta7.am0.yahoodns.net.
yahoo.com       mail exchanger = 1 mta5.am0.yahoodns.net.
yahoo.com       mail exchanger = 1 mta6.am0.yahoodns.net.
yahoo.com       nameserver = ns3.yahoo.com.
yahoo.com       nameserver = ns4.yahoo.com.
yahoo.com       nameserver = ns2.yahoo.com.
yahoo.com       nameserver = ns8.yahoo.com.
yahoo.com       nameserver = ns1.yahoo.com.
yahoo.com       nameserver = ns6.yahoo.com.
yahoo.com       nameserver = ns5.yahoo.com.

Authoritative answers can be found from:

8. Enable Debug mode

To enable Debug Mode ‘set debug’ will return you verbose information like TTL, here’s the output.

# nslookup -debug yahoo.com

> set debug
> yahoo.com
Server:         4.2.2.2
Address:        4.2.2.2#53

------------
    QUESTIONS:
        yahoo.com, type = A, class = IN
    ANSWERS:
    ->  yahoo.com
        internet address = 72.30.38.140
        ttl = 1523
    ->  yahoo.com
        internet address = 98.139.183.24
        ttl = 1523
    ->  yahoo.com
        internet address = 209.191.122.70
        ttl = 1523
    AUTHORITY RECORDS:
    ADDITIONAL RECORDS:
------------
Non-authoritative answer:
Name:   yahoo.com
Address: 72.30.38.140
Name:   yahoo.com
Address: 98.139.183.24
Name:   yahoo.com
Address: 209.191.122.70

In this article, we have tried to cover nslookup commands which may help you to search (DNS) Domain Name Service-related information.

The next article will be on the Linux dig command which is similar to nslookup. If you liked the article please share it with your friends and don’t forget to give your valuable feedback through the comment box.

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