Crestron e-Control, Справочное руководство

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Software Crestron e-Control
®
Network Classes
Internet addresses are allocated by the InterNIC, the organization that administers the
Internet. These public IP addresses are divided into
classes , the most common being
A, B, and C. The class of a network depends on its size.
You can identify the class of an IP address by looking at its first octet, as follows:
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Class A addresses are for large networks with many devices. These networks
have 0-127 as their first octet. The address 10.52.36.11 is a Class A address.
Its first octet is 10, which is between 1 and 126, inclusive.
Class A networks can have up to 16,777,214 hosts.
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Class B addresses are for medium-sized networks. These networks have 128-
191 as their first octet. The address 145.16.52.63 is a Class B address. Its first
octet is 145, which is between 128 and 191, inclusive.
Class B networks can have up to 65,534 hosts.
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Class C addresses are for small networks. These networks have 192-223 as
their first octet. The address 198.145.123.132 is a Class C address. Its first
octet is 198, which is between 192 and 223, inclusive.
Class C networks can have up to 254 hosts.
IP Subnet Masking
Applying a subnet mask to an IP address allows an Internet router to identify the
“network” and “node” parts of the address. The 1s in the mask represent the network
bits, and the 0s in the mask represent the node bits. Performing a bitwise logical
AND operation between the IP address and the subnet mask results in the network
address. For example:
10010110.11010111.00010001.00001001 150.215.017.009 (IP address)
11111111.11111111.00000000.00000000 255.255.000.000 (subnet mask)
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10010110.11010111.00000000.00000000 150.215.000.000 (network address)
This result may seem familiar because Class A, B and C addresses have a self-
encoded or default subnet mask built in:
Class A - 255.0.0.0 11111111.00000000.00000000.00000000
Class B - 255.255.0.0 11111111.11111111.00000000.00000000
Class C - 255.255.255.0 11111111.11111111.11111111.00000000
Private Subnets
Three specific ranges of IP network addresses have been set aside for internal use,
meaning that they are not routable on the Internet. These addresses are considered
unregistered . No company or agency can claim ownership of unregistered addresses
or use them on public computers. Routers are designed to discard (instead of
forward) unregistered addresses.
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Crestron e-Control® Reference Guide – DOC. 6052