DNS - Domain Name Service (6)
nslookup (exists for Unix and WinNT)
> set querytype=MX list mail servers and name servers
> set querytupe=NS list name servers
> set quarytype=A list IP addresses
> ls -d npac.syr.edu list all computers in the domain
> ls -a npac.syr.edu list all canonical names and aliases
> ls -t mx npac.syr.edu list all mx records
> netscape.com all mail servers in the domanin
> 25.117.230.128.in-addr.arpa