CCNA: Cisco Certified Network Associate — Question 1338

A network engineer must configure an interface with IP address 10.10.10.145 and a subnet mask equivalent to 11111111.11111111.11111111.11111000. Which subnet mask must the engineer use?

Answer options

• A. /29
• B. /30
• C. /27
• D. /28

Correct answer: A

Explanation

The correct subnet mask is /29, which corresponds to the binary representation of 11111111.11111111.11111111.11111000, allowing for 8 IP addresses in the subnet. The other options, /30, /27, and /28, do not match this binary format and therefore cannot be used for the given IP address.