D-Link DES-3250TG User Manual page 53

Subnetting reduces the number of possible nodes for a given
network, but increases the segmentation of the network.
Classless InterDomain Routing – CIDR
Under CIDR, the subnet mask notation is reduced to 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
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
# of Subnet Mask
Bits
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
17 255.255.255.1
28
18 255.255.255.1
92
19 255.255.255.2
DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
example
CID # of # of
R Subnets Hosts
Nota
tion
/10 2 419430
2
/11 6 209715
0
/12 14 104857
4
/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
45
in binary -
Total Hosts
8388604
12582900
14680036
15728580
16252804
16514820
16645636
16710660
16742404
16756740
16760836
16756740
16742404
16710660
16645636
16514820
16252804
15728580