# Subnetting and CIDR Activity

### Problem 1

An organization has a class C network 196.10.10 and wants to form subnets for five departments, which host as follows:

• 55 hosts
• 50 hosts
• 45 hosts
• 25 hosts
• 20 hosts
There are 195 hosts in all. Design a possible arrangement of subnets to make each department in a different subnet. For each subnet, give subnet mask and range of IP addresses.

### Problem 2

You are the CTO of a growing startup and have to get IP addresses to connect 560 computers to the Internet. You can get IP addresses from two providers, IPMart and EastSideIP. IPMart sells classA, class B and class C blocks, while EastSideIP sells CIDR blocks. As the IPv4 address space is scarce, you want to save money and get the smallest number of addresses possible.

a. If you get one block from IPMart, which class do you have to get? What is the problem with that?

b. If you get one block from EastSideIP, how many bits are there in the mask (e.g., is it a /8, /22)? How many addresses are wasted?

c. Suppose you can get two blocks from EastSideIP, and they can be of different sizes. How many bits are there in the masks for each of the blocks? How many addresses are wasted now?

Topic revision: r3 - 2015-11-10 - JimSkon

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