Homework Problem: Use of the Dig Tool

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From Computer Networking: A Top-Down Approach, Fifth Edition; Chapter 2; problem P19

P19. In this problem, we use the useful tool dig tool available on Unix and Linux hosts to explore the hierarchy of DNS servers. Recall that in Figure 2.21, a DNS server higher in the DNS hierarchy delegates a DNS query to a DNS server lower in the hierarchy, by sending back to the DNS client the name of that lower-level DNS server. First read the man page for dig, and then answer the following questions.

a. Starting with a root DNS server (from one of the root servers [a-m].root-servers.net), initiate a sequence of queries for the IP address for your department's Web server by using dig. Show the list of the names of DNS servers in the delegation chain in answering your query.

b. Repeat part a) for several popular Web sites, such as google.com, yahoo.com, or amazon.com.
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Chris DentPowerShell Developer
Top Expert 2010

Commented:

So... what's your question?

Are you having a specific problem following the questions above?

Chris

Author

Commented:
I tried the command "dig google.com -b 198.41.0.4" and got "dig: isc_socket_bind: address not available". "198.41.0.4" is the IP address for a.root-servers.net. I also tried "dig google.com -b a.root-servers.net" and got "dig: invalid address a.root-servers.net".  Because an IP address and regular URL are related I think the results of these messages could be related and I could be way off.

Anyway, the dig manual page is at http://members.shaw.ca/nicholas.fong/dig/dig-man.html.
PowerShell Developer
Top Expert 2010
Commented:

-b sets the source address, that is, the address you use to send the query from not the address you send the query to. If you're aiming the query at something you'll want to use @.

e.g.

dig google.com @198.41.0.4

Chris

Author

Commented:
Perfect! Thanks.

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