Introducing Cisco Data Center Networking (DCICN) — Question 61

What is the subnet mask for the network 172.16.0.0/21?

Answer options

• A. 255.255.0.0
• B. 255.255.255.240
• C. 255.255.248.0
• D. 255.255.255.248
• E. 255.255.248.240
• F. 255.255.255.0

Correct answer: C

Explanation

The correct subnet mask for a network with a /21 CIDR is 255.255.248.0, which allows for 2048 addresses. Other options such as 255.255.0.0 and 255.255.255.0 provide either too many or too few addresses for the specified subnet size, making them incorrect.