DX-VS1UE User’s Manual
45
Masking Point
Masked bit (Network ID)
Netmask in decimal number
1
The first bit
128.0.0.0
2
From the first bit to the second bit
192.0.0.0
3
From the first bit to the third bit
224.0.0.0
.
8
9
.
16
17
.
From the first bit to the 8
th
bit
From the first bit to the 9
th
bit
.
From the first bit to the 16
th
bit
From the first bit to the 17
th
bit
.
.
255.0.0.0
255.128.0.0
.
255.255.0.0
255.255.128.0
.
24
From the first bit to the 24
th
bit
255.255.255.0
25
From the first bit to the 24
th
bit
255.255.255.128
26
From the first bit to the 26
th
bit
255.255.255.192
27
From the first bit to the 27
th
bit
255.255.255.224
28
From the first bit to the 28
th
bit
255.255.255.240
29
From the first bit to the 29
th
bit
255.255.255.248
30
From the first bit to the 30
th
bit
255.255.255.252
31
From the first bit to the 31
st
bit
255.255.255.254
0
The 32
nd
bit
255.255.255.255
* Masking on 32
nd
bit has the same effect as masking none, and in DX-VS1UE 0 instead of 32 is used.
Masking 32 bits means that all the 32 bits are network ID, and masking none means that all the 32 bits are
host ID. Therefore masking all the 32 bits or none means that the provided IP address itself is applied with
a command of ‘Allow’ or ‘Deny’.
If you want to allow only the IP addresses from 192.168.1.61 to 192.168.70, you may set as follows
Default Policy
Deny
IP address
192.168.1.60
Masking
30
Policy
Allow
IP address
192.168.1.60
Masking
0
Policy
Deny
IP address
192.168.1.64
Masking
29
Policy
Allow
IP address
192.168.1.71
Masking
0
Policy
Deny
* The IP addresses in black squares can be any IP address of the sub-networks. In the first square,
192.168.1.60 to 192.168.1.63 is to be assigned. And in the second square 192.168.1.64 to
192.168.1.71 is to be assigned.
Principle in filtering
The sub-network range is smaller; the priority in filtering is earlier. Therefore a single IP a
ddress (masking with 0) has the first priority.
ENGLISH
