private IP address ranges

Question

What are the private IP address ranges?

Answer 1

You will find the answers to this in RFC 1918. Though, I have listed them below for you.

 10.0.0.0        -   10.255.255.255  (10/8 prefix)
 172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
 192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

It is a common misconception that 169.254.0.0/16 is a private IP address block. This is not true. It is link local, basically it is meant to be only used within networks, but it isn't official RFC1918. Additional information about IPv4 addresses can be found in RFC 3300.

On the other hand IPv6 doesn't have an equivalent to RFC1918, but any sort of site-local work should be done in fc00::/7. This is further touched on in RFC 4193.