Question

3.   Consider a sub netting network with a network ID and Mask given as 200.155.187.0/24. Determine the following for the given network address

i. To which class does this address belong to                                           (3 Marks)

ii. Identify whether the address belongs to public or private class.        (3 Marks)

iii. Calculate the new mask required to provide 10 usable hosts per subnet. (8 Marks)

iv. What is the dotted decimal notation for the given address.             (3 Marks)

v. Calculate the number of usable hosts per subnet                                (3 Marks)

Answer 1

An IP address is an identifier or label used to identify a machine on the internet or a particular network. Each of the devices on the internet must have an IP address for identification.

The netmask and subnet mask is used to divide the IP address as given below:

The netmask is a sequence of '1' followed by a sequence of '0' and it is used to divide an IP address into multiple subnets.

The subnet mask is a sequence of '1' followed by a sequence of '0' and it is used to separate a big network into smaller multiple networks.

The subnet mask is used to separate the IP address into a network address and host address.

It is made by setting '1' to all network bits and '0' to all host bits. In a network, the first and last IP addresses are used for the special purpose and remaining addresses are used as a host address.

The given IP address is:
200.155.187.0/24

i

The given address belongs to class C.

Class C:

First octet range: 192 to 223

The first three bits of the first octet is used to identify the class and always set to 110.

Subnet mask = 255.255.255.0

Note: But as per the given IP address with '/' slash means that this address is classless and not belong to any class.

ii

This address belongs to a public IP address because the range of the private address in class C is given below:

192.168.0.0 - 192.168.255.255

and this address is out of the above range

So, this address belongs to a public IP address.

iii

The given IP address is:
200.155.187.0/24

The netmask for the above address is = 11111111 11111111 11111111 00000000

For 10 usable hosts per subnet, we need to reserve the last 4 bits for the host address.

The new mask or subnet mask will be = 11111111 11111111 11111111 11110000

iv

The given IP address is:
200.155.187.0/24

The given IP address in dotted-decimal notation is = 200.155.187.0

The netmask in dotted-decimal notation is = 255.255.255.0

The subnet mask in dotted-decimal notation is = 255.255.255.240

v

The number of usable host per subnet will be = 2⁴ - 2 = 16 - 2 = 14

Because the first and the last IP addresses are used for the special purpose.