Domain Information Groper (DIG) is another helpful tool. You can use DIG to discover everything nslookup can supply.
However, DIG has one more option not available in nslookup:the ability to trace all the queries sent to DNS servers to resolve a request.
For instance, using the +trace option of DIG to examine the domain name rule11.tech:
Pro8:~$ dig @9.9.9.9 rule11.tech +trace
; <<>> DiG 9.18.12-0ubuntu0.22.04.1-Ubuntu <<>> @
; (1 server found)
;; global options: +cmd
. 3285 IN NS l
. . .
. 3285 IN NS j
. 3285 IN NS k
;; Received 687 bytes from 192.5.5.241#53(f.root
. . .
tech. 172800 IN NS b
tech. 172800 IN NS e
tech. 172800 IN NS f
tech. 172800 IN NS a
;; Received 616 bytes from 212.18.249.60#53(f.nic
rule11.tech. 3600 IN NS p
rule11.tech. 3600 IN NS p
. . .
rule11.tech. 1799 IN A
rule11.tech. 1799 IN A
rule11.tech. 1800 IN NS p
rule11.tech. 1800 IN NS p
;; Received 133 bytes from 156.154.133.100#53(pdn
This (truncated) output has three sections.
The first section shows the root server query result and the first response from a root server for the .tech TLD. The second section is the query to the TLD server and the TLD server’s response. The third section is the query to the authoritative server and the authoritative server’s response.
DIG uncovers the entire DNS query chain.
Web-Based DNS Tools
Many command-line tools for diagnosing DNS have web-based
alternatives. Figure 16-10 illustrates one, nslookup.io.
Figure 16-10 A DNS Lookup Using nslookup.io
nslookup.io allows you to choose from five different DNS
servers and returns:
• Any IPv4 addresses associated with DNS A records
• Any IPv6 addresses associated with DNS AAAA records
• How long the cached item is valid, or how much of the TTL
remains
• Any CNAME record (alias) associated with this domain name
• Any TXT records associated with this domain name
The web interface contains information not contained in Figure
• The list of authoritative DNS servers for this domain name (the NS records)
• The mail servers for this domain name (the MX records)
• The TTL and administrative contact (the SOA record)
There are positive and negative aspects to using a web-based tool or a command-line tool:
• Web-based interfaces tend to be more user friendly.
• Command-line interfaces have a “cool factor” that web-based interface do not.
• Command-line interfaces can be automated through scripts.
• Web browsers are not available on all servers or network devices.
• Command-line interfaces work in private networks (networks not connected to the global Internet).
• Command-line interfaces show what “this” host knows about domain names rather than what other hosts on the global
Internet might know.
Using a command-line interface, like DIG or nslookup, to
discover what a local host knows about a given domain name, and comparing this information to a global view from a web-based interface, is often a helpful troubleshooting technique.