200-301 · Question #805
What is the subnet address of 192.168.1.42 255.255.255.248?
The correct answer is C. 192.168.1.40/29. To find the subnet address, convert the IP address and subnet mask to binary, perform a bitwise AND operation, and determine the network address and corresponding CIDR prefix.
Question
Options
- A192.168.1.16/28
- B192.168.1.32/27
- C192.168.1.40/29
- D192.168.1.8/29
- E192.168.1.48/29
How the community answered
(24 responses)- B17% (4)
- C75% (18)
- D4% (1)
- E4% (1)
Why each option
To find the subnet address, convert the IP address and subnet mask to binary, perform a bitwise AND operation, and determine the network address and corresponding CIDR prefix.
192.168.1.16/28 corresponds to a .240 mask, not .248, and .42 would not fall into this subnet block.
192.168.1.32/27 corresponds to a .224 mask, not .248, and while .42 falls within the .32 to .63 range, the mask is incorrect.
The subnet mask 255.255.255.248 is /29. For the fourth octet, .42 in binary is 00101010, and .248 in binary is 11111000. Performing a bitwise AND (00101010 AND 11111000) yields 00101000, which is decimal 40. Thus, the subnet address is 192.168.1.40/29.
192.168.1.8/29 is a different subnet block; .42 does not fall into the .8 to .15 range for a /29.
192.168.1.48/29 is the next subnet block after 192.168.1.40/29; 192.168.1.42 falls within the 192.168.1.40 to 192.168.1.47 range.
Concept tested: Subnetting (calculating network address from IP and subnet mask)
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