nslookup stands for "name server lookup" and is a useful command for obtaining information from DNS servers. It is also very useful for troubleshooting DNS related issues and can query the DNS (Domain Name Server) and get the DNS records for any domain for the IP address.
DNS lookup example
Use the following command to find the address record for a domain. It queries the nameservers and gets the details.
# nslookup google.com
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: google.com Address: 216.58.219.206
Reverse DNS lookup
You can also use the IP address for reverse DNS lookup, and you can use the IP address to resolve the corresponding domain. Note that this is a different record configured in the reverse zone of the domain.
# nslookup 216.58.219.206
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: 206.219.58.216.in-addr.arpa name = lga25s40-in-f14.1e100.net. 206.219.58.216.in-addr.arpa name = lga25s40-in-f14.1e100.net. 206.219.58.216.in-addr.arpa name = lga25s40-in-f206.1e100.net. 206.219.58.216.in-addr.arpa name = lga25s40-in-f206.1e100.net.
Query a specific DNS server
You can also query a specific DNS server. Additional parameters need to be passed for the nameserver IP address or domain name. For example, to query the 8.8.4.4 name server, use the following command.
# nslookup google.com 8.8.4.4
Server: 8.8.4.4 Address: 8.8.4.4#53 Non-authoritative answer: Name: google.com Address: 216.58.219.206
Find the SOA record for a domain
Use nslookup to find the SOA (Start of Authorization) record for any domain. For example, to find the SOA records for the domain google.com, you can use the following command. Type-type=soa needs to be specified as a command line parameter.
# nslookup -type=soa google.com
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: google.com origin = ns4.google.com mail addr = dns-admin.google.com serial = 159912615 refresh = 900 retry = 900 expire = 1800 minimum = 60 Authoritative answers can be found from:
origin: The authority of the source of information.
mail addr: The email address of the domain administrator (the first dot represents the @ symbol in the email address).
serial: Revision data of the domain area, in the format of YYYYMMDDNN.
refresh: The referh interval (in seconds) at which the secondary name server will check the primary name server for updated versions of the zone.
retry: The time to wait for a secondary name server before trying to reconnect to the primary name server after a failed attempt.
expire: The time in seconds for the secondary name server cache to expire.
minimum: The time in seconds that the secondary name server's cache should not be flushed if no time has elapsed since the last flush.
Find a domain’s MX records
You can also query the MX (Mail Exchange) records for any domain, which are responsible for the delivery of email.
# nslookup -query=mx google.com
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: google.com mail exchanger = 10 aspmx.l.google.com. google.com mail exchanger = 30 alt2.aspmx.l.google.com. google.com mail exchanger = 50 alt4.aspmx.l.google.com. google.com mail exchanger = 40 alt3.aspmx.l.google.com. google.com mail exchanger = 20 alt1.aspmx.l.google.com. Authoritative answers can be found from:
Finding TXT records for a domain
TXT records are useful for many types of records (such as DKIM, SPF, etc.). You can use the command below to find all TXT records configured for any domain.
# nslookup -query=txt google.com
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: google.com text = "v=spf1 include:_spf.google.com ~all" Authoritative answers can be found from:
Find all records for a domain
Use -query=any to list all records for any domain.
# nslookup -query=any google.com
Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: google.com Address: 216.58.219.206 google.com has AAAA address 2607:f8b0:4006:80e::200e google.com mail exchanger = 20 alt1.aspmx.l.google.com. google.com mail exchanger = 40 alt3.aspmx.l.google.com. google.com nameserver = ns2.google.com. google.com nameserver = ns4.google.com. google.com nameserver = ns3.google.com. google.com rdata_257 = 0 issue "pki.goog" google.com mail exchanger = 30 alt2.aspmx.l.google.com. google.com mail exchanger = 10 aspmx.l.google.com. google.com mail exchanger = 50 alt4.aspmx.l.google.com. google.com text = "v=spf1 include:_spf.google.com ~all" google.com nameserver = ns1.google.com. google.com rdata_257 = 0 issue "symantec.com" google.com origin = ns2.google.com mail addr = dns-admin.google.com serial = 159912615 refresh = 900 retry = 900 expire = 1800 minimum = 60 Authoritative answers can be found from:
Nslookup in interactive mode
We can also use nslookup in interactive mode. To enter interactive mode, type nslookup on the console and press Enter. You will get an nslookup prompt such as >. Here, you can run the same query and get the domain's information from the DNS server. Comments have been added between commands for better understanding.
root@tecadmin:~#nslookup ### Type domain name to get information from dns server > google.com Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: google.com Address: 172.217.10.46 ### Set the another specific dns server to query. > server 8.8.4.4 Default server: 8.8.4.4 Address: 8.8.4.4#53 ### Again try to get the dns information, This time nslookup connects to specified dns server. > google.com Server: 8.8.4.4 Address: 8.8.4.4#53 Non-authoritative answer: Name: google.com Address: 172.217.10.46 ### Set the query type. for example to get MX information set query=mx > set query=mx ### Again try to get the dns information, This time nslookup will show MX information for domain > google.com Server: 8.8.4.4 Address: 8.8.4.4#53 Non-authoritative answer: google.com mail exchanger = 30 alt2.aspmx.l.google.com. google.com mail exchanger = 50 alt4.aspmx.l.google.com. google.com mail exchanger = 40 alt3.aspmx.l.google.com. google.com mail exchanger = 10 aspmx.l.google.com. google.com mail exchanger = 20 alt1.aspmx.l.google.com. Authoritative answers can be found from:
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