| Exam 200-301 | Question id=5333 | Network Fundamentals |
You are the network administrator for your company. You have a Class B address range and are planning for a network that allows 150 hosts per subnet and at least 164 subnets. Which subnet mask should you use to accomplish the task?
| A. |
255.255.192.0 | |
| B. |
255.255.255.192 | |
| C. |
255.255.255.0 | |
| D. |
255.255.255.252 |
You should use 255.255.255.0 as the subnet mask to allow 150 hosts per subnet and at least 164 subnets. The formulas used to calculate the number of subnets and hosts are:
Number of subnets = 2number-of-subnet-bits
Number of hosts per subnet = 2number-of-host-bits - 2
Subnet mask in decimal: 255.255.255.0
Subnet mask in binary: 11111111.11111111.11111111.00000000
Number of subnet bits: 8 (binary 1s in the subnet octet of the subnet mask)
Number of host bits: 8 (binary 0s in the subnet mask)
In this scenario, we find that for 255.255.255.0:
Subnets that can be used: 28 = 256
Hosts that can be used: 28 - 2 = 254
The other options do not allow 150 hosts per subnet and at least 164 subnets.