24 Port Gigabit Ethernet PoE Switch – User Manual Page 12 of 72
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Class C:
IP address range between 192.0.0.0 and 223.255.255.255. Each class C network
has a 24-bit network prefix followed 8-bit host address. There are 2,097,152 (2^21)/24
networks able to be defined with a maximum of 254 (2^8 –2) hosts per network.
Class D and E:
Class D is a class with first 4 MSB (Most significance bit) set to 1-1-1-0 and is used
for IP Multicast. See also RFC 1112. Class E is a class with first 4 MSB set to 1-1-1-1 and
is used for IP broadcast.
According to IANA (Internet Assigned Numbers Authority), there are three specific
IP address blocks reserved and able to be used for extending internal network. We call it
Private IP address and list below:
Please refer to RFC 1597 and RFC 1466 for more information.
Subnet mask:
It means the sub-division of a class-based network or a CIDR block. The subnet is
used to determine how to split an IP address to the network prefix and the host address
in bitwise basis. It is designed to utilize IP address more efficiently and ease to manage
IP network.
For a class B network, 128.1.2.3, it may have a subnet mask 255.255.0.0 in de-
fault, in which the first two bytes is with all 1s. This means more than 60 thousands of
nodes in flat IP address will be at the same network. It’s too large to manage practically.
Now if we divide it into smaller network by extending network prefix from 16 bits to, say
24 bits, that’s using its third byte to subnet this class B network. Now it has a subnet
mask 255.255.255.0, in which each bit of the first three bytes is 1. It’s now clear that the
first two bytes is used to identify the class B network, the third byte is used to identify
the subnet within this class B network and, of course, the last byte is the host number.
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