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212.0.0 - 213.255.255 RIPE NCC
214.0.0 - 215.255.255 US Department of Defense
216.0.0 - 216.255.255 ARIN
217.0.0 - 217.255.255 RIPE NCC
218.0.0 - 218.255.255 APNIC
219.0.0 - 222.255.255 APNIC
The ranges defined as Others are to be where flexibility outside the
constraints of regional boundaries is required. The range defined as
multi-regional includes the Class C networks that were assigned before this
new scheme was adopted. The 192 networks were assigned by the InterNIC
and the 193 networks were previously allocated to RIPE in Europe.
► Where an organization has a range of Class C network numbers, the range
provided is assigned as a bit-wise contiguous range of network numbers, and
the number of networks in the range is a power of 2. That is, all IP addresses
in the range have a common prefix, and every address with that prefix is
within the range. For example, a European organization requiring 1500 IP
addresses would be assigned eight Class C network numbers (2048 IP
addresses) from the number space reserved for European networks (194.0.0
through 195.255.255) and the first of these network numbers would be
divisible by eight. A range of addresses satisfying these rules is 194.32.136
through 194.32.143, in which case the range consists of all of the IP
addresses with the 21-bit prefix 194.32.136, or B '110000100010000010001'.
The maximum number of network numbers assigned contiguously is 64,
corresponding to a prefix of 18 bits. An organization requiring more than 4096
addresses but less than 16,384 addresses can request either a Class B or a
range of Class C addresses. In general, the number of Class C networks
assigned is the minimum required to provide the necessary number of IP
addresses for the organization on the basis of a two-year outlook. However,
in some cases, an organization can request multiple networks to be treated
separately. For example, an organization with 600 hosts is normally assigned
four Class C networks. However, if those hosts were distributed across 10
LANs with between 50 and 70 hosts per LAN, such an allocation can cause
serious problems, because the organization would have to find 10 subnets
within a 10-bit local address range. This means at least some of the LANs
have a subnet mask of 255.255.255.192, which allows only 62 hosts per LAN.
The intent of the rules is not to force the organization into complex subnetting
of small networks, and the organization should request 10 different Class C
numbers, one for each LAN.
1 Information for this and the following numbers in this list are from:
http://www.iana.org/assignments/ipv4-address-space
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