RFC 1918: Address Allocation for Private Internets (rfc-editor.org)....All you ever wanted to know about private addresses.
But a shorter answer will be as follows:
Your private (internal) ranges are:
10.0.0.0 - 10.255.255.255 (10.0.0.0 /8)
172.16.0.0 - 172.31.255.255 (172.16.0.0 /12)
182.168.0.0 - 192.168.255.255 (192.168.0.0 /16)
Those are your private ranges, and specifically a /30 would have a subnet mask of 255.255.255.252. So for example, you could use 10.0.0.0 /30 and your subnet would look like this:
Subnet Number: 10.0.0.0
Usable IP's: 10.0.0.1 - 2
Broadcast Address: 10.0.0.3
You could then move to the next range:
Subnet Number: 10.0.0.4
Usable IP's: 10.0.0.5 - 6
Broadcast Address: 10.0.0.7
HTH, please rate if that helps.
Richard W. Pidcock