User`s guide

Signamax 065-7931 16-Port 10/100/1000BaseT/TX WebSmart Switch
19
In this diagram, you can see the subnet mask that is 25 bits long,
255.255.255.128, contains 126 members in the sub-netted network. Another
concept to be remembered is that the length of the network prefix equals the
number of the bits with 1s in that subnet mask. Using this information, the number
of IP addresses matched can be easily counted. The following table shows the
result.
Prefix Length No. of IP matched No. of Addressable IP
/32
1 -
/31
2 -
/30
4 2
/29
8 6
/28
16 14
/27
32 30
/26
64 62
/25
128 126
/24
256 254
/23
512 510
/22
1024 1022
/21
2048 2046
/20
4096 4094
/19
8192 8190
/18
16384 16382
/17
32768 32766
/16
65536 65534
Table 2-3
According to the scheme above, a subnet mask 255.255.255.0 will partition a
class C network. It means there will be a maximum of 254 effective nodes existing
in this sub-netted network and it is considered a physical network in an autonomous
network. It therefore owns a network IP address which may look like 168.1.2.0.
Using subnet masking, a large network can be cut into smaller pieces of
network. If we want to have more than two independent networks in an Enterprise
network, a partition to the network must be performed. In this case, a subnet mask
must be applied.