Basic DNS Tools

FreeBSD includes several tools for inspecting DNS information. Since most DNS runs over UDP (User Datagram Protocol, see Chapter 6), you cannot use telnet to manually query a server as we will do with email and web services later. Your only access to live DNS information is through host(1) and dig(1).

The host(1) Command

Use host(1) for a quick forward DNS check (finding the IP address of a known hostname). For example, to check my publisher's web page, I do the following:

# host www.nostarch.com
www.nostarch.com has address 72.32.92.4

This is perhaps the simplest DNS query you can have: "Here's a hostname, what's its IP address?" Other seemingly simple queries generate more complicated results.

# host www.cnn.com
 www.cnn.com is ...

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