Answers to Written Lab 3

157

# Answers to Written Lab 3

1.

172.16.10.5 255.255.255.128: Subnet is 172.16.10.0, broadcast is 172.16.10.127, and valid host range is 172.16.10.1 through 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: Subnet is 172.16.10.32, broadcast is 172.16.10.63, and valid host range is 172.16.10.33 through 10.62.

256 – 224 = 32. 32 + 32 = 64—bingo. 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: Subnet is 172.16.10.64, broadcast is 172.16.10.127, and valid host range is 172.16.10.65 through 172.16.10.126.

256 – 192 = 64. 64 + 64 = 128, so the network address must be 172.16.10.64, with a broad- cast of 172.16.10.127.

4.

172.16.10.17 255.255.255.252: Subnet is 172.16.10.16, broadcast is 172.16.10.19, and valid hosts are 172.16.10.17 and 18.

256 – 252 = 4. 4 + 4 = 8, plus 4 = 12, plus 4 = 16, plus 4 = 20—bingo. The subnet is 172.16.10.16, and the broadcast must be 10.19.

5.

172.16.10.33 255.255.255.240: Subnet is 172.16.10.32, broadcast is 172.16.10.47, and valid host range is 172.16.10.33 through 46.

256 – 240 = 16. 16 + 16 = 32, plus 16 = 48. Subnet is 172.16.10.32; broadcast is 172.16.10.47.

6.

192.168.100.25 255.255.255.252: Subnet is 192.168.100.24, broadcast is 192.168.100.27, and valid hosts are 192.168.100.25 and 26.

256 – 252 = 4. 4 + 4 = 8, plus 4 = 12, plus 4 = 16, plus 4 = 20, plus 4 = 24, plus 4 = 28. Subnet is 100.24; broadcast is 100.27.

7.

192.168.100.37 255.255.255.248: Subnet is 192.168.100.32, broadcast is 192.168.100.39, and valid host range is 192.168.100.33 through 38.

256 – 248 = 8. 8 + 8 = 16, 24, 32, 40. Subnet is, then, 100.32, with a broadcast of 100.39 because 40 is the next subnet.

8.

192.168.100.66 255.255.255.224: Subnet is 192.168.100.64, broadcast is 192.168.100.95, and valid host range is 192.168.100.65 through 94.

256 – 224 = 32. 32 + 32 = 64, plus 32 = 96. Subnet is 100.64, and broadcast is 100.95.

9.

192.168.100.17 255.255.255.248: Subnet is 192.168.100.16, broadcast is 192.168.100.23, and valid host range is 192.168.100.17 through 22.

256 – 248 = 8. 8 + 8 = 16, plus 8 = 24. Subnet is 16, and broadcast is 23.

10. 10.10.10.5 255.255.240.0: Subnet is 10.10.0.0, broadcast is 10.10.15.255, and valid hosts are 10.10.0.1 through 10.10.15.254.