Answers to Subnetting and Creating Custom Subnet Masks Practice Problems

 

Answers assume Non-RFC 1812 networks (must subtract 2 from the number of Host IDs).

 

Specify The Correct Default Subnet Mask for the Following Addresses:

Review:  Default Subnet Masks

 

Recommended Process

Determine address class of address.

            Determine appropriate default subnet mask.

           

                                                Default Subnet Mask

210.23.67.102                       255.255.255.0

66.23.148.0                           255.0.0.0

158.23.251.33                       255.255.0.0

144.23.117.254                    255.255.0.0

192.254.23.123                    255.255.2550

144.207.78.1                         255.255.0.0

63.125.23.211                       255.0.0.0

192.25.128.36                       255.255.255.0

128.12.254.98                       255.255.0.0

134.223.156.89                    255.255.0.0

127.0.0.1                                255.0.0.0

224.23.108.23                       N/A – Multicast Address

223.78.27.144                       255.255.255.0

77.123.28.167                       255.0.0.0

191.249.222.234                  255.255.0.0

 

Determine the Appropriate Custom Subnet Masks:

Review:  Subnetting and Custom Subnet Masks

 

Recommended Process

Determine address class of address.

            First determine appropriate default subnet mask.

            Second determine the appropriate custom subnet mask that provides:

                        Subnets >= Physical Segments

                        Host IDs >= Hosts per Physical Segment

 

 

Scenario 1

 

Required Number of Physical Segments:

5

Maximum Number of Hosts/Physical Segment:

5000

Network Address:

152.77.0.0

 

 

Proposed Custom Subnet Mask:

255.255.224.0

Number of Subnets Supported:

6

Maximum Number of Host IDs per Subnet:

8190

 

 

Scenario 2

 

Required Number of Physical Segments:

100

Maximum Number of Hosts/Physical Segment:

88,000

Network Address:

39.0.0.0

 

 

Proposed Custom Subnet Mask:

255.254.0.0

Number of Subnets Supported:

126

Maximum Number of Host IDs per Subnet:

131,070

 

Scenario 3

 

Required Number of Physical Segments:

100

Maximum Number of Hosts/Physical Segment:

350

Network Address:

177.133.0.0

 

 

Proposed Custom Subnet Mask:

255.255.254.0

Number of Subnets Supported:

126

Maximum Number of Host IDs per Subnet:

510

 

Scenario 4

 

Required Number of Physical Segments:

4

Maximum Number of Hosts/Physical Segment:

1,500,000

Network Address:

120.0.0.0

 

 

Proposed Custom Subnet Mask:

255.224.0.0

Number of Subnets Supported:

6

Maximum Number of Host IDs per Subnet:

2,097,150

 

Scenario 5

 

Required Number of Physical Segments:

16

Maximum Number of Hosts/Physical Segment:

1,500

Network Address:

128.199.0.0

 

 

Proposed Custom Subnet Mask:

255.255.248.0

Number of Subnets Supported:

30

Maximum Number of Host IDs per Subnet:

2,046

 

Scenario 6

 

Required Number of Physical Segments:

250

Maximum Number of Hosts/Physical Segment:

100

Network Address:

191.254.0.0

 

 

Proposed Custom Subnet Mask:

255.255.255.0

Number of Subnets Supported:

254

Maximum Number of Host IDs per Subnet:

254

 

Scenario 7

 

Required Number of Physical Segments:

12

Maximum Number of Hosts/Physical Segment:

12

Network Address:

216.122.44.0

 

 

Proposed Custom Subnet Mask:

255.255.255.240

Number of Subnets Supported:

14

Maximum Number of Host IDs per Subnet:

14

 

Scenario 8

 

Required Number of Physical Segments:

10

Maximum Number of Hosts/Physical Segment:

750,000

Network Address:

12.0.0.0

 

 

Proposed Custom Subnet Mask:

255.240.0.0

Number of Subnets Supported:

14

Maximum Number of Host IDs per Subnet:

1,048,574

 

Scenario 9

 

Required Number of Physical Segments:

50

Maximum Number of Hosts/Physical Segment:

600

Network Address:

134.119.0.0

 

 

Proposed Custom Subnet Mask:

255.255.252.0

Number of Subnets Supported:

62

Maximum Number of Host IDs per Subnet:

1022

 

Scenario 10

 

Required Number of Physical Segments:

5

Maximum Number of Hosts/Physical Segment:

25

Network Address:

192.177.4.0

 

 

Proposed Custom Subnet Mask:

255.255.255.224

Number of Subnets Supported:

6

Maximum Number of Host IDs per Subnet:

30

 

Determine Subnet IDs and Ranges of Host IDs

Review:  Subnetting and Custom Subnet Masks

 

Recommended Process

Determine address class of address.

            First determine appropriate default subnet mask.

            Second determine the appropriate custom subnet mask that provides:

                        Subnets >= Physical Segments

                        Host IDs >= Hosts per Physical Segment

            Determine the Subnet IDs

            Determine the ranges of Host IDs

 

Example

 

Scenario 1

 

 

Required Number of Physical Segments:

5

 

Maximum Number of Hosts/Physical Segment:

5000

 

Network Address:

152.77.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.224.0

 

Number of Subnets Supported:

6

 

Maximum Number of Host ID per Subnet:

8190

 

Subnet IDs:

152.77.0.0  (Invalid)

152.77.32.0

152.77.64.0

152.77.96.0

152.77.128.0

152.77.160.0

152.77.192.0 

152.77.224.0 (Invalid)

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

152.77.32.0

152.77.64.0

152.77.96.0

152.77.128.0

152.77.160.0

152.77.192.0

152.77.32.1 – 152.77.63.254

152.77.64.1 – 152.77.95.254

152.77.96.1 – 152.77.127.254

152.77.128.1 – 152.77.159.254

152.77.160.1 – 152.77.191.254

152.77.192.1 – 152.77.223.254

 

 

 

 

Scenario 2

 

 

Required Number of Physical Segments:

100

 

Maximum Number of Hosts/Physical Segment:

88,000

 

Network Address:

39.0.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.254.0.0

 

Number of Subnets Supported:

126

 

Maximum Number of Host ID per Subnet:

131,070

 

Subnet IDs:

39.2.0.0

39.4.0.0

39.6.0.0

39.8.0.0

……

39.254.0.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

39.2.0.0

39.4.0.0

39.6.0.0

39.8.0.0

……

39.252.0.0

39.2.0.1 – 39.3.255.254

39.4.0.1 – 39.5.255.254

39.6.0.1 – 39.7.255.254

39.8.0.1 – 39.9.255.254

……

39.252.0.1 – 39.253.255.254

 

 

Scenario 3

 

 

Required Number of Physical Segments:

100

 

Maximum Number of Hosts/Physical Segment:

350

 

Network Address:

177.133.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.254.0

 

Number of Subnets Supported:

126

 

Maximum Number of Host ID per Subnet:

510

 

Subnet IDs:

177.133.2.0

177.133.4.0

177.133.6.0

177.133.8.0

…..

177.133.252.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

177.133.2.0

177.133.4.0

177.133.6.0

177.133.8.0

…..

177.133.252.0

177.133.2.1 – 177.133.3.254

177.133.4.1 – 177.133.5.254

177.133.6.1 – 177.133.7.254

177.133.8.1 – 177.133.9.254

…..

177.133.252.1 – 177.133.253.254

 

 

Scenario 4

 

 

Required Number of Physical Segments:

4

 

Maximum Number of Hosts/Physical Segment:

1,500,000

 

Network Address:

120.0.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.224.0.0

 

Number of Subnets Supported:

6

 

Maximum Number of Host ID per Subnet:

2,097,150

 

Subnet IDs:

120.32.0.0

120.64.0.0

120.96.0.0

120.128.0.0

120.160.0.0

120.192.0.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

120.32.0.0

120.64.0.0

120.96.0.0

120.128.0.0

120.160.0.0

120.192.0.0

120.32.0.1 – 120.63.255.254

120.64.0.1 – 120.95.255.254

120.96.0.1 – 120.127.255.254

120.128.0.1 – 120.159.255.254

120.160.0.1 – 120.191.255.254

120.192.0.1 – 120.223.255.254

 

 

 

Scenario 5

 

 

Required Number of Physical Segments:

16

 

Maximum Number of Hosts/Physical Segment:

1,500

 

Network Address:

128.199.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.248.0

 

Number of Subnets Supported:

30

 

Maximum Number of Host ID per Subnet:

2,046

 

Subnet IDs:

128.199.8.0

128.199.16.0

128.199.24.0

128.199.32.0

…..

128.199.240.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

128.199.8.0

128.199.16.0

128.199.24.0

128.199.32.0

…..

128.199.240.0

128.199.8.1 – 128.199.15.254

128.199.16.1 – 128.199.23.254

128.199.24.1 – 128.199.31.254

128.199.32.1 – 128.199.39.254

…..

128.199.240.1 – 128.199.247.254

 

 

Scenario 6

 

 

Required Number of Physical Segments:

250

 

Maximum Number of Hosts/Physical Segment:

100

 

Network Address:

191.254.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.255.0

 

Number of Subnets Supported:

254

 

Maximum Number of Host ID per Subnet:

254

 

Subnet IDs:

191.254.1.0

191.254.2.0

191.254.3.0

191.254.4.0

……

191.254.254.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

191.254.1.0

191.254.2.0

191.254.3.0

191.254.4.0

……

191.254.254.0

191.254.1.1 – 191.254.1.254

191.254.2.1 – 191.254.2.254

191.254.3.1 – 191.254.3.254

191.254.4.1 – 191.254.4.254

……

191.254.254.1 – 191.254.254.254

 

 

 

Scenario 7

 

 

Required Number of Physical Segments:

12

 

Maximum Number of Hosts/Physical Segment:

12

 

Network Address:

216.122.44.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.255.240

 

Number of Subnets Supported:

14

 

Maximum Number of Host ID per Subnet:

14

 

Subnet IDs:

216.122.44.16

216.122.44.32

216.122.44.48

216.122.44.64

…….

216.122.44.224

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

216.122.44.16

216.122.44.32

216.122.44.48

216.122.44.64

…….

216.122.44.224

216.122.44.17 – 216.122.44.30

216.122.44.33 – 216.122.44.46

216.122.44.49 – 216.122.43.62

216.122.44.65 – 216.122.43.78

…….

216.122.44.225 – 216.122.44.238

 

 

Scenario 8

 

 

Required Number of Physical Segments:

10

 

Maximum Number of Hosts/Physical Segment:

750,000

 

Network Address:

12.0.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.240.0.0

 

Number of Subnets Supported:

14

 

Maximum Number of Host ID per Subnet:

1,048,574

 

Subnet IDs:

12.16.0.0

12.32.0.0

12.48.0.0

12.64.0.0

…..

12.224.0.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

12.16.0.0

12.32.0.0

12.48.0.0

12.64.0.0

…..

12.224.0.0

12.16.0.1 – 12.31.255.254

12.32.0.1 – 12.47.255.254

12.48.0.1 – 12.63.255.254

12.64.0.1 – 12.79.255.254

…..

12.224.0.1 – 12.239.255.254

 

 

 

Scenario 9

 

 

Required Number of Physical Segments:

50

 

Maximum Number of Hosts/Physical Segment:

600

 

Network Address:

134.119.0.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.252.0

 

Number of Subnets Supported:

62

 

Maximum Number of Host ID per Subnet:

1022

 

Subnet IDs:

134.119.4.0

134.119.8.0

134.119.12.0

…..

134.119.248.0

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

134.119.4.0

134.119.8.0

134.119.12.0

…..

134.119.248.0

134.119.4.1 – 134.119.7.254

134.119.8.1 – 134.119.11.254

134.119.12.1 – 134.119.15.254

…..

134.119.248.1 – 134.119.251.254

 

 

 

Scenario 10

 

 

Required Number of Physical Segments:

3

 

Maximum Number of Hosts/Physical Segment:

25

 

Network Address:

192.177.4.0

 

 

 

 

Proposed Custom Subnet Mask:

255.255.255.224

 

Number of Subnets Supported:

6

 

Maximum Number of Host ID per Subnet:

30

 

Subnet IDs:

192.177.4.32

192.177.4.64

192.177.4.96

…..

192.177.4.192

 

 

 

1st Host – Last Host on Subnet

Host ID Ranges per Subnet

192.177.4.32

192.177.4.64

192.177.4.96

…..

192.177.4.192

192.177.4.33 – 192.177.4.62

192.177.4.65 – 192.177.4.94

192.177.4.97 – 192.177.4.126

…..

192.177.4.193 – 192.177.4.222

 

 

 

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