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IT 120
Spring 2010
Homework 7 Solutions
1.
We wish to assign a CIDR block of 512 addresses (including all 0’s and all 1’s), starting at
128.211.200.0.
a.
What is the maximum address in this block?
?
[Hint:
figure out how many bits are
required to represent 512 hosts.
The maximum address is when all those bits are 1]
512 addresses run from 0 00000000 to 1 11111111
10000000 11010011 11001000 00000000
+
1 11111111
10000000 11010011 11001001 11111111
128.211.201.255 is the maximum address
b.
How many bits are in the host_id?
The host id is 9 bits, as calculated above.
c.
How many bits are in the net_id?
net id = 32 bits total – 9 bits host id = 23 bits net id
d.
What is the mask in binary, dotted decimal, and slash notation?
11111111 11111111 11111110 00000000
255.255.254.0
/23
2.
A CIDR block extends from 112.45.156.0
to 112.45.159.255.
a.
How many bits are in the net id?
min = 01110000 00101101
10011100 00000000
max = 01110000 00101101 10011111 11111111
The first 22 bits are identical, so the net id is 22 bits.
b.
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 Spring '10
 Joan
 Networking

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