Reserved addresses are a bank of IP addresses set aside for Intranet use. They are not registered to any network, and hence, are not routable across the Internet. RFC 1597 and its replacement, RFC 1918, are the documents that specify the range of reserved addresses. At this writing, these ranges are 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 173.31.255.255, and 192.168.0.0 to 192.168.255.255.