Samsung Webthru SWC 306 User Manual page 25

E
In C class network, the applied number of IP addresses with network masking is as below when you mask on
host ID part (X4: the fourth byte).
Masking on X4 Byte
25 26 27
128 64 32
(192) (224)
(128)
Free Free
Masked
Masked Free
Masked
Masked
Masked
Masked
The most common case is to make subnet through network masking, and it is to divide a network into some
smaller network. If provided IP address is 192.168.1.2, you may divide the whole network into 2 sub-
networks and allow or deny only the IP addresses that belong to one of sub-networks.
With setting as follows, The IP address of 192.168.1.2 is divided into two sub-networks and allow for the IP
address out of the first sub-network to assess Webthru.
•
Default Policy: Deny
•
IP address: 192.168.1.2
•
Masking: 25 (255.255.255.128)
•
Then only the IP addresses from 192.168.1.0 to 192.168.1.127 are to access Webthru, while the IP
addresses from 192.168.1.128 to 192.168.1.255 and any other IP address are to be denied accessing
Webthru.
Changing IP address can reverse the result. If you set IP address as 192.168.1.130, only the IP addresses from
192.168.1.128 to 192.168.1.255 are to access Webthru. And the IP addresses from 192.168.1.0 to
192.168.1.127 and any other IP address are to be denied accessing Webthru.
You may refer below table to figure out masking point from network information that is given from your ISP
or network administrator.
Masking Point
1
2
3
.
8
9
.
16
240 to 255
28 29 30
16 8 4
(240) (248) (252)
Free Free Free
Free Free Free
Free Free Free
Free Free
Free
Masked
Masked
Masked bit (Network ID)
The first bit
From the first bit to the second bit
From the first bit to the third bit
.
From the first bit to the 8
From the first bit to the 9
.
From the first bit to the 16
Reserved for specific utilization
Remark
31 0 Masking Point
2 1 Decimal Number
(254) (255) (Accumulated Value)
Free Free 7 digits are free
Free Free 6 digits are free
Free Free 5 digits are free
Free Free 4 digits are free
Free Free 3 digits are free
Free Free 2 digits are free
Free 1 digits are free
No free digit
Netmask in decimal number
th
bit
th
bit
th
bit
25
Webthru SWC 306 User's Guide
Host ID
number
2 7 = 128
6
2 = 64
5
2 = 32
2 4 = 16
3
2 = 8
2
2 = 4
1
2 = 2
0
2 = 1
128.0.0.0
192.0.0.0
224.0.0.0
.
255.0.0.0
255.128.0.0
.
255.255.0.0