DX-VS1UE User’s Manual
44
mask on host ID part (X4: the fourth byte).
Masking on X4 Byte
Remark
Host ID number
25
26
27
28
29
30
31
0
Masking Point
128
(128)
64
(192)
32
(224)
16
(240)
8
(248)
4
(252)
2
(254)
1
(255)
Decimal Number
(Accumulated
Value)
Masked
Free
Free
Free
Free
Free
Free
Free
7 digits are free
2
7
= 128
Masked
Free
Free
Free
Free
Free
Free
6 digits are free
2
6
= 64
Masked
Free
Free
Free
Free
Free
5 digits are free
2
5
= 32
Masked
Free
Free
Free
Free
4 digits are free
2
4
= 16
Masked
Free
Free
Free
3 digits are free
2
3
= 8
Masked
Free
Free
2 digits are free
2
2
= 4
Masked
Free
1 digits are free
2
1
= 2
Masked
No free digit
2
0
= 1
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 192.168.1.100, 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 192.168.1.100 is divided into two sub-networks and allow
for the IP address out of the first sub-network to access DX-VS1UE.
•
Default Policy: Deny
•
IP address: 192.168.1.100
•
Masking: 25 (255.255.255.128)
•
Then only the IP addresses from 192.168.1.0 to 192.168.1.127 are to access DX-VS1UE, while
the IP addresses from 192.168.1.128 to 192.168.1.255 and any other IP address are to be denied
accessing DX-VS1UE.
Changing IP address can reverse the result. If you set IP address as 192.168.1.130, only the IP ad-
dresses from 192.168.1.128 to 192.168.1.255 are to access DX-VS1UE. And the IP addresses from
192.168.1.0 to 192.168.1.127 and any other IP address are to be denied accessing DX-VS1UE.
You may refer below table to figure out masking point from network information that is given from
your ISP or network administrator.
ENGLISH
