DNS lookups

To find a hostname when you know the IP address:

nmblookup -A <ip_address>

eg. nmblookup -A 192.168.0.148

or

host <ip_address>

eg. host 192.168.0.148

To find an IP address when you know the hostname, try the following ways:

whois www.google.com
dig www.google.com
nslookup www.google.com