IPv4 subnetting worksheet with answers

Free printable IPv4 subnetting worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy

How many usable host addresses H are there in an IPv4 subnet with prefix /27?

/27

H =

2.Easy

Write the subnet mask of a /21 network in dotted-decimal notation. What is the value x of its third octet?

/21

x =

3.Medium

The network 192.168.129.0/24 is divided into /27 subnets, numbered 1, 2, 3, … from the lowest address (subnet 1 starts at .0). What is the fourth octet x of the network address of subnet 5?

192.168.129.0/24/27subnet 5 (subnet 1 starts at .0)

x =

4.Medium

The network 192.168.119.0/24 is divided into /25 subnets, numbered 1, 2, 3, … from the lowest address (subnet 1 starts at .0). What is the fourth octet x of the broadcast address of subnet 2?

192.168.119.0/24/25subnet 2 (subnet 1 starts at .0)

x =

5.Hard

A router has routes to these networks: 10.120.0.0/24, 10.120.1.0/24, 10.120.2.0/24, 10.120.3.0/24, 10.120.4.0/24, 10.120.5.0/24, 10.120.6.0/24. What is the longest prefix length p of a single summary route that covers all of them?

10.120.0.0/24 … 10.120.6.0/24

p =

6.Hard

A host has the address 10.20.51.35/30. What is the last number (fourth octet) x of its subnet's broadcast address?

10.20.51.35/30

x =

Answer key

1. H = 30
2. x = 248
3. x = 128
4. x = 255
5. p = 21
6. x = 35

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