Question

The topic is about (Subnetting in computer networks).

Your help is greatly appreciated!

University of Southern Ontario has been assigned a Class B address with a network number of 132.27.0.0. You are asked to come up with a subnetting scheme that allows to create 650 subnets on that network. Show your work. 1) How many bits must be borrowed for the subnet ID? 2) What is the subnet mask required? 3) How many hosts there can be on each subnet? 4) How many subnets can there be? 5) Explain in 4 lines MAX, how subnetting helps in this case save IP addresses.

Answer 1

Part a :
No of subnets to create = 650 which maeans we want to divide our network int 650 parts .
Eg : If I want to divide the network (132.27.0.0 ) in two parts then we can do it using 1 bit as follows :
132.127.00000000. 0 and132.127.10000000. 0

In order to divide into 650 subnets : No of bits required = log₂ (650) =9.somthing =10.

Therefore, No of bits must be borrowed for subnet ID = 10.

Part b:
Subnet mask : In subnet mask we represent each Network ID and subnet ID bit as '1' whereas Host ID bit as '0'.
As it (132.27.0.0) belongs to class B so No of Network Id Bits =16, Subnet Id bit =10 (As calculated above ) and Host Id bits = 32-16-10 = 6

Therefore, Subnet Mask = 11111111. 11111111. 11111111. 11000000

Part c :
As no of host Id bits = 6
So no of hosts = 2⁶ = 64 but out of these two are reserved for Network ID (All 0 host bits ) and limited broadcast address (All 1 host bits ).
Therefore, No. of hosts =64 -2 =62   

Part d:
As no of bits borrowe for subnet ID  = 10.
With these bits, we can represent 2¹⁰ subnets.

Therefore, No of subnets that can be there =1024.  

Part e:
Suppose If a person wants a network with 300 devices (IP addresses ) then in that case person will be alloted with class B ( as class C only provides 254 devices or Host or IP addresses ). No of hosts in class B = 2¹⁶ -2 whereas the person wants only 300 IP addresses so there will be a waste of thousands of IP addresses if subnetting was not there. By subnetting, we can select the number of bits in oursubnetwork, creating more realistic host limits.In this way, we are saving no of IP addresses using subnetting.
There are also advantages of subnetting some of them are as follows :

• As we are dividing a bigger network into smaller networks (650 subnets ) so maintaince becomes easy.
• Security is there as one smaller network can be protected easily from the others.
• Performance and speed of network will improve.