DNS on Windows Server 2003, 3rd Edition

Finding Out a Host’s Aliases

One thing you can’t easily do with nslookup—or any query tool, for that matter—is find out a host’s aliases. With the host table, it’s easy to find both the canonical name of a host and any aliases. No matter which you look up, they’re all there together on the same line, as shown in the following excerpt from HOSTS:

192.249.249.3  terminator.movie.edu terminator bigt

With DNS, however, if you look up the canonical name, all you get is the canonical name. There’s no easy way for the name server or the application to know whether aliases exist for that canonical name:

C:\> nslookup 
Default Server:  wormhole.movie.edu 
Address:  192.249.249.1 

> terminator 
Server:  wormhole.movie.edu 
Address:  192.249.249.1 

Name:    terminator.movie.edu 
Address:  192.249.249.3

If you use nslookup to look up an alias, you’ll see that alias and the canonical name. nslookup reports both the alias and the canonical name in the packet. But you won’t see any other aliases that might point to that canonical name:

C:\> nslookup 
Default Server:  wormhole.movie.edu 
Address:  192.249.249.1 

> bigt 
Server:  wormhole.movie.edu 
Address:  192.249.249.1 

Name:    terminator.movie.edu 
Address:  192.249.249.3 
Aliases:  bigt.movie.edu

You can find out all the CNAMEs for a host in a particular zone by transferring the whole zone and picking out the CNAME records in which that host is the canonical name. You can have nslookup filter on CNAME records:

C:\> nslookup  Default Server: wormhole.movie.edu Address: ...