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Authors:
James F. Kurose, Keith W. Ross
Chapter:
Application Layer
Exercise:
Problems
Question:21 | ISBN:9780132856201 | Edition: 6

Question

Suppose that your department has a local DNS server for all computers in the department. You are an ordinary user (i.e., not a network/system administra- tor). Can you determine if an external Web site was likely accessed from a computer in your department a couple of seconds ago? Explain.

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Answer

Yes, we can use dig to query that Web site in the local DNS server.

For example, “dig cnn.com” will return the query time for finding cnn.com. If cnn.com was just accessed a couple of seconds ago, an entry for cnn.com is cached in the local DNS cache, so the query time is 0 msec. Otherwise, the query time is large. 

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