D-Link DES-3326 User Manual - page 89
DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
Switch Management and Operating Concepts
75
CIDR allows IP address space to be assigned in a way that the total
number of available IP addresses in the assigned space more
closely matches the network’s actual needs. This method has been
adapted for use in intranetworks from the Internet.
Under CIDR, the subnet mask notation is reduced to a simplified
shorthand. Instead of spelling out the bits of the subnet mask, it is
simply listed as the number of “1”s (bits) in the network portion of
the address. The subnet mask of the above example looks like this
in binary - 11111111.11100000.00000000.00000000 – and there are
11 “1”s or 11 bits used to mask the network address from the node
address. So the example written in CIDR notation becomes:
10.32.0.0/11
This is the reason that non-contiguous bits are not recommended
in subnet masks.
CIDR notation can also be used for classed addresses: Class A = /8,
Class B = /16, and Class C = /24.
# of
Bits
Subnet Mask
CIDR
Notation
# of
Subnets
# of
Hosts
Total
Hosts
2 255.192.0.0
/10
2
4194302
8388604
3 255.224.0.0
/11
6
2097150
12582900
4 255.240.0.0
/12
14
1048574
14680036
5 255.248.0.0
/13
30
524286 15728580
6 255.252.0.0
/14
62
262142 16252804
7 255.254.0.0
/15
126 131070 16514820
8 255.255.0.0
/16
254 65534 16645636
9 255.255.128.0 /17
510 32766 16710660
10 255.255.192.0 /18
1022 16382 16742404
11 255.255.224.0 /19
2046 8190 16756740
12 255.255.240.0 /20
4094 4094 16760836
13 255.255.248.0 /21
8190 2046 16756740
14 255.255.252.0 /22
16382 1022 16742404
15 255.255.254.0 /23
32766 510
16710660
16 255.255.255.0 /24
65534 254
16645636