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I know – for example – that there are two DNS names for an IP. However nslookup ip only returns one record.

How do I get all the records for an IP?

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I think the real world analogy would be: You can't know for sure how many phone books actually list your number. – slhck Sep 24 '11 at 17:20
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DNS itself does not have a way to query names by value. When you run nslookup ip, you are simply querying for PTR records at a special reversed-ip.in-addr.arpa domain.

Usually, when a host or address has many names, only one PTR record with the primary name is added – often for security/privacy reasons (in case of shared website hosting), or just because their owner didn't care enough.

The only authoritative source in most cases is therefore the IP address owner themselves. (But also note that the owner might not always know about other domains pointing to their address. In DNS, if someone owns a domain they can point it anywhere.)

Several sites exist which collect information about what websites are hosted at a particular IP address (such as yougetsignal), but they have no way of knowing 100% complete information. If there is no website hosted on a particular domain name, it won't be listed in such databases.

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Yet another answer to bookmark to upvote. . . – surfasb Sep 24 '11 at 18:50
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