Lab Objective:
Learn how to use the dig command and some of its switches.
Lab Purpose:
Dig is short for domain information groper. It’s a Unix command line tool used to query DNS name servers. It comes with a large number of options and switches you can use, and it varies according to the platform (e.g., Red Hat, Ubuntu, etc.), so check your documentation.
Lab Tool:
Ubuntu VM
Lab Topology:
Please use the following topology to complete this lab exercise. I used a virtual Ubuntu PC running inside VirtualBox, but if you are using Windows, you can use your home PC. Just check your firewall settings don’t block the test.
Lab Walkthrough:
Task 1:
Pull up a terminal by typing ‘terminal’ into the search box.
Task 2:
At the command prompt, issue the dig command. Check your documentation for more information on all the available switches. Ubuntu doesn’t display anything after the question mark.
Task 3:
Issue a dig cisco.com command. By default, an A record search will be executed.
We got one answer: 3145 is the time to live (TTL) before the DNS server rechecks the entry. ‘IN’ indicates a standard Internet class, A record is the standard record type, and 72.163.4.185 is the IP address the domain name resolves to.
Task 4:
We can use one of the many switches available. Let’s use the mx switch to query the mail servers.
Task 5:
The ANY switch will return all information record types. Many users have had very few results here, so don’t worry if the same happens to you.
Task 6:
You can drill down to use the AAAA record if you wish with the dig -t AAAA command, where ‘t’ is short for ‘type’.
Task 7:
Finally, you can do a reverse lookup with the -x switch and the IP address.
Note:
There are many other options for this command, so feel free to research further.
