RADVision VIU-323, Руководство пользователя

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Appendix C
C-2
The first four bits of an address determine its class. These can be represented by decimals,
making it easy to identify the class of a given IP address. The following table illustrates the
decimal range of the first octet of each class:
Class Decimal Range
A 0 to 127
B 128 to 191
C 192 to 223
D 224 to 239
1
Within a company or organization you can assign any IP address to equipment connected to
the network. However, if you plan to connect to the Internet, it is important to obtain
registered addresses to conform to the international addressing standards. On the Internet, IP
addresses must be unique.
You can obtain registered IP addresses from your Internet Service Provider (ISP). Because
of the limited number of registered network IP addresses, you can use Private Network
addresses for all hosts that don’t directly connect to the Internet. Private Network addresses
are certain IP addresses that have been set aside for this purpose. Classes A, B and C have
several addresses reserved for private use:
Class Private Network Addresses
A 10.0.0.0 – 10.255.255.255
B 172.16.0.0 – 172.31.255.255
C 192.168.0.0 – 192.168.255.255
If you have a big organization, you can obtain one Class C registered network address for
the routers and firewalls that connect to the Internet and use a private network Class B
address internally.
Subnets and Using a Subnet Mask
You can further divide your network into subnets or sub-networks by using a subnet-
addressing scheme. Subnet addressing is a mechanism that increases the number of
available IP network addresses. This is important for large networks divided into network
segments by routers or bridges because a unique network address must be assigned to each
network segment.
1
240 to 255 are reserved for Class E addresses. These are intended for future use.