IT 420
Spring 2011
Homework 7
1.
We wish to create 20 subnets in a Class C network.
Assume that we wish to use the
minimum number of bits for the subnet id.
a.
How many bits will be used for the subnet id?
5 bits
4 bits is too small because 2
10
= 20, but five bits is enough be
b.
How many possible hosts are there on each subnet?
number of host bits = 20 total – 20 class B net id – 5 subnet id = 5 bits
2
10

2= 2 hosts
c.
What is the mask in binary notation?
11111111 11111000 11111111 00000000
2.
A Class B network uses 4 bits for a subnet id.
a.
How many possible subnets are there? 16
b.
How many bits will be in the hostid? 4
c.
How many possible hosts are there on each subnet? 254
d.
What is the mask in binary notation?
11111111111111111111111111111111
3.
We wish to assign a CIDR block of 256 addresses (including all 0’s and all 1’s), starting at
128.211.200.0.
a.
How many bits are in the host_id?
b.
What is the maximum address in this block?
[Hint:
The maximum address is when
all host id bits are 1]
c.
How many bits are in the net_id?
d.
What is the mask in binary, dotted decimal, and slash notation?
4.
A CIDR block extends from 112.45.156.0
to 112.45.159.255.
a.
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 Spring '09
 IP address, Subnetwork, bytes, datagram

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