There are three address ranges designated as private as per [http://tools.ietf.org/html/rfc1918 RFC 1918]:

* <code>10.x0.x0.x 0</code> … <code>10.255.255.255</code> (<code>10/8</code>) - (Class A networks network that start with <code>10.</code>)* <code>172.16.x0.x 0</code> … <code>172.31.255.255</code> (<code>172.16/12</code>) - (Class B networks that start with <code>172.16.</code>)* <code>192.168.0.0</code> … <code>192.168.1255.x 255</code> (<code>192.168/16</code>) - (Class C networks that start with <code>192.168.1.</code>)