24 Port Gigabit Ethernet PoE Switch – User Manual Page 13 of 72
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Not all IP address is available in the sub-netted network. Two special addresses are
reserved. They are the addresses with all zero’s and all one’s host number. For example,
an IP address 128.1.2.128, what IP address reserved will be looked like? All 0s mean the
network itself, and all 1s mean IP broadcast.
In this diagram, you can see the subnet mask with 25-bit long, 255.255.255.128,
contains 126 members in the sub-netted network. Another is that the length of network
prefix equals the number of the bit with 1s in that subnet mask. With this, you can easily
count the number of IP addresses matched. The following table shows the result.
Table 2-3
According to the scheme above, a subnet mask 255.255.255.0 will partition a net-
work with the class C. It means there will have a maximum of 254 effective nodes exist-
ed in this sub-netted network and is considered a physical network in an autonomous
network. So it owns a network IP address which may looks like 168.1.2.0.
With the subnet mask, a bigger network can be cut into small pieces of network. If
we want to have more than two independent networks in a worknet, a partition to the
network must be performed. In this case, subnet mask must be applied.
For different network applications, the subnet mask may look like 255.255.255.240.