Answer to Question #315838 in Computer Networks for Avi

Question

An organization is granted a block of addresses with the beginning address

150.25.0.0/24. The organization needs to have 3 subblocks of addresses to use in its three

subnets: one subblock of 11 addresses, one subblock of 40 addresses, and one subblock of

125 addresses. Design the network and plot it completely with respective subnets, IP range,

Network IDs. In detail with diagram

Answer 1

beginning address 150.25.0.0/24

/24 means that

Network Address:                 150.25.0.0

Usable Host IP Range:          150.25.0.1 - 150.25.0.254

Broadcast Address:               150.25.0.255

Total Number of Hosts:        256

Number of Usable Hosts:      254

Subnet Mask:                        255.255.255.0

1). subblock of 11 addresses

 

Subblock can has total 8 host (6 Usable Hosts), the next is 16 host (14 Usable Hosts - first IP (Network Address) and last IP (Broadcast Address) not usable).

Network with “/z” (-.-.-.zzz) subnet mask has number of hosts = 2^{(32 – z)}, and it is = 256 - zzz.

2⁴ = 16, 32 – z = 4, z = 28

256 – 16 = 240

 

Possible /28 Networks for 150.25.0.*

Network Address/Usable Host Range/Broadcast Address:

150.25.0.0/150.25.0.1 - 150.25.0.14/150.25.0.15

150.25.0.16/150.25.0.17 - 150.25.0.30/150.25.0.31

150.25.0.32/150.25.0.33 - 150.25.0.46/150.25.0.47

150.25.0.48/150.25.0.49 - 150.25.0.62/150.25.0.63

150.25.0.64/150.25.0.65 - 150.25.0.78/150.25.0.79

150.25.0.80/150.25.0.81 - 150.25.0.94/150.25.0.95

150.25.0.96/150.25.0.97 - 150.25.0.110/150.25.0.111

150.25.0.112/150.25.0.113 - 150.25.0.126/150.25.0.127

150.25.0.128/150.25.0.129 - 150.25.0.142/150.25.0.143

150.25.0.144/150.25.0.145 - 150.25.0.158/150.25.0.159

150.25.0.160/150.25.0.161 - 150.25.0.174/150.25.0.175

150.25.0.176/150.25.0.177 - 150.25.0.190/150.25.0.191

150.25.0.192/150.25.0.193 - 150.25.0.206/150.25.0.207

150.25.0.208/150.25.0.209 - 150.25.0.222/150.25.0.223

150.25.0.224/150.25.0.225 - 150.25.0.238/150.25.0.239

150.25.0.240/150.25.0.241 - 150.25.0.254/150.25.0.255

 

So

Network Address:                150.25.0.0

Usable Host IP Range:          150.25.0.1 - 150.25.0.14

Broadcast Address:               150.25.0.15

Total Number of Hosts:        16

Number of Usable Hosts:      14

Subnet Mask:                        255.255.255.240

CIDR Notation:                    /28

 

 

2). subblock of 40 addresses

 

Subblock can has total 32 host (30 Usable Hosts), the next is 64 host (62 Usable Hosts - first IP (Network Address) and last IP (Broadcast Address) not usable).

2⁶ = 64, 32 – z = 6, z = 26

256 – 64 = 192

 

Possible /26 Networks for 150.25.0.*

Network Address/Usable Host Range/Broadcast Address:

150.25.0.0/150.25.0.1 - 150.25.0.62/150.25.0.63

150.25.0.64/150.25.0.65 - 150.25.0.126/150.25.0.127

150.25.0.128/150.25.0.129 - 150.25.0.190/150.25.0.191

150.25.0.192/150.25.0.193 - 150.25.0.254/150.25.0.255

 

So

Network Address:                150.25.0.64

Usable Host IP Range:          150.25.0.65 - 150.25.0.126

Broadcast Address:               150.25.0.127

Total Number of Hosts:        64

Number of Usable Hosts:      62

Subnet Mask:                        255.255.255.192

CIDR Notation:                    /26

 

 

3). subblock of 125 addresses

 

Subblock can has total 64 host (62 Usable Hosts), the next is 128 host (126 Usable Hosts - first IP (Network Address) and last IP (Broadcast Address) not usable).

2⁷ = 128, 32 – 7 = 25, z = 25

256 – 128 = 128

 

Possible /25 Networks for 150.25.0.*

Network Address/Usable Host Range/Broadcast Address:

150.25.0.0/150.25.0.1 - 150.25.0.126/150.25.0.127

150.25.0.128/150.25.0.129 - 150.25.0.254/150.25.0.255

 

Network Address:                150.25.0.128

Usable Host IP Range:          150.25.0.129 - 150.25.0.254

Broadcast Address:               150.25.0.255

Total Number of Hosts:        128

Number of Usable Hosts:      126

Subnet Mask:                        255.255.255.128

CIDR Notation:           /25