User`s guide

Signamax 

 065-7726SPOE / 065-7726SPOE-FP 24-Port 10/100BaseT/TX
PoE Managed Switch User Manual
Publication date: February 2010
Revision A1.0
24
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.
Prefix Length
No. o
f 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
163
84
16382
/17
32768
32766
/16
65536
65534
Table 2-4
According to the scheme above, a subnet mask 255.255.255.0 will partition a network
with the class C. It means there will have a maximum of 254 effective nodes existed 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.