The network administrator is asked to configure 113 point-to-point links. Which IP addressing scheme defines the address range and subnet mask that meet the requirement and waste the fewest subnet and host addresses?

Question:
The network administrator is asked to configure 113 point-to-point links. Which IP addressing scheme defines the address range and subnet mask that meet the requirement and waste the fewest subnet and host addresses?

• 10.10.0.0/16 subnetted with mask 255.255.255.252
• 10.10.0.0/18 subnetted with mask 255.255.255.252
• 10.10.1.0/24 subnetted with mask 255.255.255.252
• 10.10.0.0/23 subnetted with mask 255.255.255.252
• 10.10.1.0/25 subnetted with mask 255.255.255.252

Explanation: We need 113 point-to-point links which equal to 113 sub-networks < 128 so we need to borrow 7 bits (because
2^7 = 128).
The network used for point-to-point connection should be /30.
So our initial network should be 30 ?7 = 23.
So 10.10.0.0/23 is the correct answer.
You can understand it more clearly when writing it in binary form:
/23 = 1111 1111.1111 1110.0000 0000
/30 = 1111 1111.1111 1111.1111 1100 (borrow 7 bits)

Exam with this question: CCNA v3.0 (200-125) Study Guide – Exam Dumps