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E.g. IP address in decimal: 192. 168. 1. 13 (It is equal to 11000000. 10101000. 00000001. 00001101)
* Binary number 1 means to take the equivalent decimal number (2
Network masking point is to be expressed with decimal number from 0 to 31. IP address is consisted in 4
bytes. 4 bytes are 32 bits. Network is to be masked on every bit from the first bit to the 32
marked with binary number '1', and the corresponding bits out of provided IP address are defined as network
ID for IP filtering.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 0
E.g. Network masking on the 8
E.g. Network masking on the 16
E.g. Network masking on the 24
E.g. Network masking on the 32
According to masking point, masked network ID is to be different out of the same IP address. For example, if
IP address is described as 192.168.1.13 (11000000.10101000.00000001.00001101) with masking point 24
(255.255.255.0),
the
'11000000.10101000.00000001.xxxxxxxx' (2
Webthru.
If you describe an IP address as 192.168.1.13 and put masking point 26 (255.255.255.192), the masked bits
are the first 26 digits and network ID masked as '11000000.10101000.00000001.00'. In this case, the IP
addresses whose IP address is consisted with '11000000.10101000.00000001.00xxxxxx' (2
addresses) will be applied with a command of 'Allow' or 'Deny'.
Applied IP address number according to masking point
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 0
31
30
29
28
27
26
25
2
2
2
2
2
2
2
E.g. Masking point 8: 2
E.g. Masking point 16: 2
E.g. Masking point 24: 2
E.g. Masking point 0: 2
Though masking point is to be any bit out of 32 bits, it is common to point on the bits of host ID part. If the
masking point is placed on network ID part, the range is expanded compared to the provided IP address.
Network class is divided as follows. D and E class networks are not to be used by normal user.
Class
A
B
C
D
Network masking point (0 to 31)
th
bit (8): 11111111. 0000000. 00000000. 00000000 (255.0.0.0)
th
bit (16): 11111111. 11111111. 00000000. 00000000 (255.255.0.0)
th
bit (24): 11111111. 11111111. 11111111. 00000000 (255.255.255.0)
nd
bit (0): 11111111. 11111111. 11111111. 11111111 (255.255.255.255)
IP
addresses
8
24
23
22
21
20
19
18
2
2
2
2
2
2
2
Decimal number of X1 byte
0 to 127
128 to 191
192 to 223
224 to 239
7
5
, 2
whose
IP
(256) pieces of IP addresses) will be allowed or denied from
17
16
15
14
13
12
11
2
2
2
2
2
2
2
2
24
pieces of IP addresses are applied
16
pieces of IP addresses are applied
8
pieces of IP addresses are applied
0
pieces of IP address (itself) is applied
Network ID
X1
X1, X2
X1, X2, X3
For Multicasting utilization
24
, etc) and 0 means to disregard it.
nd
bit. Masked bit is
address
is
consisted
6
(64) pieces of IP
10
9
8
7
6
5
4
2
2
2
2
2
2
2
Host ID
X2, X3, X4
X3, X4
X4
Webthru SWC 306 User's Guide
with
3
2
1
0
2
2
2
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