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Subnetting Subnetting Practice Examples: Class C Addresses with Answers Practice example 1: Network address: 192.168.10.0 Subnet mask: 255.255.255.224
1. How many subnets? Ans: 6
2. How many hosts? Ans: 30
3. What are the valid subnets? Ans: 32, 64, 96, 128, 160, 192
4. Fill in the table below. Subnet 1 32
Subnet 2 64
Subnet 3 96
Subnet 4 128
Subnet 5 160
Subnet 6 192
33
65
97
129
161
193
62 63
94 95
126 127
158 159
190 191
222 223
Meaning The subnet address The first valid host
Our last valid host The broadcast address
Practice example 2: Network address: 192.168.10.0 Subnet mask: 255.255.255.240
1. How many subnets? Ans: 14
2. How many hosts? Ans: 14
3. What are the valid subnets? Ans: 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224
4. Fill in the table below. Subnet
16
32
48
64
80
96
112 128 144 160 176 192 208 224
First Host
17
33
49
65
81
97
113 129 145 161 177 193 209 225
Last Host
30
46
62
78
94
110
126
142
158
174
190
206
222
238
Broadcast
31
47
63
79
95
111
127
143
159
175
191
207
223
239
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Practice example 3: Network address: 192.168.10.0 Subnet mask: 255.255.255.248
1. How many subnets? Ans: 30
2. How many hosts? Ans: 6
3. What are the valid subnets? Ans: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120, 128, 136, 144, 152, 160, 168, 176, 184, 192, 200, 208, 216, 224, 232, 240
4. Fill in the table below (only the first three and last three subnets). Subnet
8
16 24 224 232 240
First Host
9
17 25 225 233 241
Last Host
14 22 30 230 238 246
Broadcast 15 23 31 231 239 247
Practice example 4: Network address: 192.168.10.0 Subnet mask: 255.255.255.252
1. How many subnets? Ans: 62
2. How many hosts? Ans: 2
3. What are the valid subnets? Ans: 4, 8, 12 etc., all the way to 248
4. Fill in the table below (only the first three and last three subnets). Subnet
4
8
12 240 244 248
First Host
5
9
13 241 245 249
Last Host
6
10 14 242 246 250
Broadcast 7
11 15 243 247 251
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Further Subnetting Practice with Answers Write the subnet, broadcast address and valid host range for the following: 1. 172.16.10.5
255.255.255.128
Ans: Subnet is 172.16.10.0, broadcast is 172.16.10.127 and valid host range is 172.16.10.1 to 126. You need to ask yourself, “Is the subnet bit in the fourth octet on or off?” If the host address has a value of less than 128 in the fourth octet, then the subnet bit must be off. If the value of the fourth octet is higher than 128, then the subnet bit must be on. In this case, the host address is 10.5 and the bit in the fourth octet must be off. The subnet must be 172.16.10.0.
2. 172.16.10.33
255.255.255.224
Ans: Subnet is 172.16.10.32, broadcast is 172.16.10.63 and valid host range is 172.16.10.33 to 10.62. 256-224=32. 32+32=64. The subnet is 10.32 and the next subnet is 10.64, so the broadcast address must be 10.63.
3. 172.16.10.65
255.255.255.192
Ans: Subnet is 172.16.10.64, broadcast is 172.16.10.127 and valid host range is 172.16.10.65 to 172.16.10.126. 256-192=64. 64+64=128, so the network address must be 172.16.10.64, with a broadcast of 172.16.10.127.
4. 172.16.10.17
255.255.255.252
Ans: Network is 172.16.10.16, broadcast is 172.16.10.19 and valid host range is 172.16.10.17 to 18. 256-252=4. 4+4=8, plus 4=12, plus 4=16, plus 4=20. So the subnet is 172.16.10.16 and the broadcast must be 10.19.
5. 172.16.10.33
255.255.255.240
Ans: Network is 172.16.10.32, broadcast is 172.16.10.47 and valid host range is 172.16.10.33 to 46. 256-240=16. 16+16=32, plus 16=48. The subnet is 172.16.10.32 and the broadcast is 172.1610.47.
6. 192.168.100.25
255.255.255.252
Ans: Subnet is 192.168.100.24, broadcast is 192.168.100.27 and valid host range is 192.168.100.25 to 26. 256-252=4. 4+4=8, plus 4=12, plus 4=16, plus 4=20, plus 4=24, plus 4=28. The subnet is 100.24 and the broadcast is 100.27.
7. 192.168.100.17, with 4 bits of subnetting Ans: Subnet is 192.168.100.16, broadcast is 192.168.100.31 and valid host range is 192.168.100.17 to 30. 256-240=16. 16+16=32. The subnet is, then, 100.16 and the broadcast is 100.31 because 32 is the next subnet.
8. 192.168.100.66, with 3 bits of subnetting Ans: Subnet is 192.168.100.64, broadcast is 192.168.100.95 and valid host range is 192.168.100.65 to 94. 256-224=32. 32+32=64, plus 32=96. The subnet is 100.64 and the broadcast is 100.95.
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http://www.soc.staffs.ac.uk/alh2/CNI/tutorials/tutorial_7a_ans.doc 9. 192.168.100.17
255.255.255.248
Ans: Subnet is 192.168.100.16, broadcast is 192.168.100.23 and valid host range is 192.168.100.17 to 22. 256-248=8. 8+8=16, plus 8=24. The subnet is 16 and the broadcast is 23.
10. 10.10.10.5
255.255.255.252
Ans: Subnet is 10.10.10.4, broadcast is 10.10.10.7 and valid host range is 10.10.10.5 to 6. 256-252=4. 4+4=8.
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