User's Manual
24
Webthru SWC 306 User’s Guide
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
7
, 2
5
, etc) and 0 means to disregard it.
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
nd
bit. Masked bit is
marked with binary number ‘1’, and the corresponding bits out of provided IP address are defined as network
ID for IP filtering.
Network masking point (0 to 31)
123456789101112131415161718192021222324252627282930310
E.g. Network masking on the 8
th
bit (8): 11111111. 0000000. 00000000. 00000000 (255.0.0.0)
E.g. Network masking on the 16
th
bit (16): 11111111. 11111111. 00000000. 00000000 (255.255.0.0)
E.g. Network masking on the 24
th
bit (24): 11111111. 11111111. 11111111. 00000000 (255.255.255.0)
E.g. Network masking on the 32
nd
bit (0): 11111111. 11111111. 11111111. 11111111 (255.255.255.255)
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 IP addresses whose IP address is consisted with
‘11000000.10101000.00000001.xxxxxxxx’ (2
8
(256) pieces of IP addresses) will be allowed or denied from
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
6
(64) pieces of IP
addresses) will be applied with a command of ‘Allow’ or ‘Deny’.
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 Decimal number of X1 byte Network ID Host ID
A 0 to 127 X1 X2, X3, X4
B 128 to 191 X1, X2 X3, X4
C 192 to 223 X1, X2, X3 X4
D 224 to 239 For Multicasting utilization
Applied IP address number according to masking point
1 2 3 4 5 6 7 8 9 10111213141516171819202122232425262728293031 0
2
31
2
30
2
29
2
28
2
27
2
26
2
25
2
24
2
23
2
22
2
21
2
20
2
19
2
18
2
17
2
16
2
15
2
14
2
13
2
12
2
11
2
10
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
E.g. Masking point 8: 2
24
pieces of IP addresses are applied
E.g. Masking point 16: 2
16
pieces of IP addresses are applied
E.g. Masking point 24: 2
8
pieces of IP addresses are applied
E.g. Masking point 0: 2
0
pieces of IP address (itself) is applied