SignaMax 065-7940C-WS, Руководство пользователя

Страница: 27 / 115

Signamax
™
065-7840C-WS 24-Port 10/100/1000BaseT/TX WebSmart Switch
Publication date: June, 2011
Revision 1.0
17
network, and, of course, the last byte is the host number.
Not all IP address is available in the sub-netted network. Two special
addresses are reserved. They are the addresses with all zero’s and all one’s host
number. For example, an IP address 128.1.2.128, what IP address reserved will be
looked like? All 0s mean the network itself, and all 1s mean IP broadcast.
In this diagram, you can see the subnet mask that is 25-bits long,
255.255.255.128, contains 126 members in the sub-netted network. Another is that
the length of the network prefix equals the number of the bits with 1s in that subnet
mask. Knowing this, you can easily count the number of IP addresses matched. The
following table shows the result:
Prefix Length No. of IP matched No. of Addressable IP
/32
1 -
/31
2 -
/30
4 2
/29
8 6
/28
16 14
/27
32 30
/26
64 62
/25
128 126
/24
256 254
/23
512 510
/22
1024 1022
/21
2048 2046
/20
4096 4094
/19
8192 8190
/18
16384 16382
/17
32768 32766
10000000.00000001.00000010.1 0000000
128.1.2.128/25
25 bits
1 0000000
1 1111111
All 0s = 128.1.2.128
All 1s= 128.1.2.255
Subnet Network