CIDR Expansions

• Expand the following CIDR

192.168.224.0/19

fixed = 19
variable = 13

              192.168.111xxxxx.xxxxxxxx
SM: 11111111.11111111.11100000.00000000

start: 192.168.224.0
end:   192.168.255.255

10.128.0.0/10

10.128.0.0/10


fixed = 10
variable= 22
          10.10xxxxxx.xxxxxxxx.xxxxxxxx
SM: 11111111.11000000.00000000.00000000

start: 10xxxxxx  =>   10000000 10.128.0.0
end: 10xxxxxx=>       10111111 10.191.255.255


172.16.240.0/22

fixed = 22
variable = 10
               172.16.111100xx.xxxxxxxx
SM: 11111111.11111111.11111100.00000000

start = 172.16.11110000.0 => 172.16.240.0
end  = 172.16.11110011.255 => 172.16.243.255

Design a network with 2 subnets of 200 devices each

• Subnets = 2
• Subnet size = 200
• Network = 2 * 200
• Solution

private:

192.168.0.0/16
10.0.0.0/8
172.16.0.0/12

Network

Size ~= 400

2^v  ~= 400

variable = 9
fixed = 32-9 = 23

CIDR = 172.16.0.0/23
SM:    11111111.11111111.11111110.00000000

Subnet: 

Size ~= 200

2^v ~= 200
variable =8
fixed = 24


SM: 11111111.11111111.11111111.00000000

Network SM: 11111111.11111111.11111110.00000000
Subnet SM:  11111111.11111111.11111111.00000000
------------------------------------------------
                       172.16.0000000y.xxxxxxxx
             subnet 1: 172.16.00000000.xxxxxxxx  = 172.16.0.0/24
             subnet 2: 172.16.00000001.xxxxxxxx  = 172.16.1.0/24
             Network: 172.16.0.0/23

Design a network with 4 subnets of 100 devices each

• subnets = 4
• each subnet = 100
• network = 400

private:

192.168.0.0/16
10.0.0.0/8
172.16.0.0/12

Network

size = 400

2^v ~= 400
v= 9
fixed = 23

network: 192.168.0.0/23
SM: 11111111.11111111.11111110.00000000

Subnet:
size = 100

2^v ~= 100
v=7
fixed = 25

Network SM: 11111111.11111111.11111110.00000000
Subnet  SM: 11111111.11111111.11111111.10000000
-------------------------------------------------
                                     y.y
            Subnet 1: 192.168.00000000.0xxxxxxx = 192.168.0.0/25
            Subnet 2: 192.168.00000000.1xxxxxxx = 192.168.0.128/25
            Subnet 3: 192.168.00000001.0xxxxxxx = 192.168.1.0/25
            Subnet 4: 192.168.00000001.1xxxxxxx = 192.168.1.128/25

Design a Network with 4 subnets size 1000

• subnets = 4
• subnet size = 1000
• network size = 4000
• Solution

private:

192.168.0.0/16
10.0.0.0/8
172.16.0.0/12

Network

size = 4000

2^v ~= 4000
v= 12
fixed = 20

ip:             10.0.0.0/20
SM: 11111111.11111111.11110000.00000000

Subnet:
size = 1000

2^v ~= 1000
v=10
fixed = 22

Network SM: 11111111.11111111.11110000.00000000
Subnet  SM: 11111111.11111111.11111100.00000000
-------------------------------------------------
                                  yy
               Subnet 1: 10.0.000000xx.xxxxxxxx => 10.0.0.0/22
               Subnet 2: 10.0.000001xx.xxxxxxxx => 10.0.4.0/22
               Subnet 3: 10.0.000010xx.xxxxxxxx => 10.0.8.0/22
               Subnet 4: 10.0.000011xx.xxxxxxxx => 10.0.12.0/22