I got about halfway through typing this entry tonight, and it occurred to me to check Wikipedia. Lo and behold, a colorful grid laying out all sorts of info!

http://en.wikipedia.org/wiki/Reserved_IP_addresses

There are 16 total reserved networks, and 15 of them are covered in the excellent RFC 5735. The sixteenth address block, 100.64.0.0/10, is a newcomer. RFC 6598 was written in April 2012. The address space is intended for Carrier-Grade NAT (which is horrifying), but it does say “However, it may be used in a manner similar to RFC 1918 private address space”. Interesting!

Let’s break down that big Wikipedia table:

Private Network Address Ranges

IP Range         # Addresses
10.0.0.0/8        16,777,216  
172.16.0.0/12      1,048,576 
192.168.0.0/16        65,536 

Local Address Ranges

IP Range         # Addresses    Notes
0.0.0.0/8         16,777,216    For broadcast messages to current network
127.0.0.0/8       16,777,216    For loopback addresses to local host
169.254.0.0/16        65,536    For autoconfiguration between 2 hosts on a single link

Address Ranges for Documentation and Example Code

IP Range         # Addresses
192.0.2.0/24             256 
198.51.100.0/24          256
203.0.113.0/24           256

Special-Purpose Address Ranges

IP Range         # Addresses    Notes
100.64.0.0/10      4,194,304    For carrier-grade NAT, but may be used for private networks
192.0.0.0/29               8    For DS-Lite transition mechanism
192.88.99.0/24           256    For 6to4 anycast relays
198.18.0.0/15        131,072    For benchmark tests of routers
224.0.0.0/4      268,435,456    For multicast
240.0.0.0/4      268,435,455    For future use
255.255.255.255/32         1    For limited broadcast