D-Link DGS-3308 Series User Manual page 32

Classless InterDomain Routing – CIDR
Under CIDR, the subnet mask notation is reduced to a simplified shorthand. Instead of specifying all of the bits of the
subnet mask, it is simply listed as the number of contiguous "1"s (bits) in the network portion of the address. Look at the
subnet mask of the above example in binary - 11111111.11100000.00000000.00000000 – and you can see that there are
11 "1"s or 11 bits used to mask the network address from the node address. Written in CIDR notation this becomes:
10.32.0.0/11
# Subnet Mask
of
Bit
s
2 255.192.0.0
3 255.224.0.0
4 255.240.0.0
5 255.248.0.0
6 255.252.0.0
7 255.254.0.0
8 255.255.0.0
9 255.255.128.0
10 255.255.192.0
11 255.255.224.0
12 255.255.240.0
13 255.255.248.0
14 255.255.252.0
15 255.255.254.0
16 255.255.255.0
17 255.255.255.128
18 255.255.255.192
19 255.255.255.224
20 255.255.255.240
21 255.255.255.248
22 255.255.255.252
Table 5-2. Class A Subnet Masks
# of Subnet Mask CIDR
Bits Notatio
n
2 255.255.192 /18
3 255.255.224.0 /19
4 255.255.240.0 /20
5 255.255.248.0 /21
6 255.255.252.0 /22
7 255.255.254.0 /23
8 255.255.255.0 /24
9 255.255.255.12 /25
8
10 255.255.255.19 /26
2
11 255.255.255.22 /27
4
12 255.255.255.24 /28
0
13 255.255.255.24 /29
8
14 255.255.255.25 /30
CID # of # of Hosts
R Subnets
Not
atio
n
/10 2 4194302
/11 6 2097150
/12 14 1048574
/13 30 524286
/14 62 262142
/15 126 131070
/16 254 65534
/17 510 32766
/18 1022 16382
/19 2046 8190
/20 4094 4094
/21 8190 2046
/22 16382 1022
/23 32766 510
/24 65534 254
/25 131070 126
/26 262142 62
/27 525286 30
/28 1048574 14
/29 2097150 6
/30 4194302 2
# of # of
Subnets Hosts
2 16382
6 8190
14 4094
30 2046
62 1022
126 510
254 254
510 126
1022 62
2046 30
4094 14
8190 6
16382 2
22
8-port Gigabit Ethernet Switch User's Guide
Total Hosts
8388604
12582900
14680036
15728580
16252804
16514820
16645636
16710660
16742404
16756740
16760836
16756740
16742404
16710660
16645636
16514820
16252804
15728580
14680036
12582900
8388604
Total
Hosts
32764
49140
57316
61380
63364
64260
64516
64260
63364
61380
57316
49140
32764