CCNA

Refer to the exhibit. What is the most efficient summarization that R1 can use to advertise its networks to R2?

A. 172.1.0.0/22

B. 172.1.0.0/21

C. 172.1.4.0/22

D. 172.1.4.0/24
172.1.5.0/24
172.1.6.0/24
172.1.7.0/24

E. 172.1.4.0/25
172.1.4.128/25
172.1.5.0/24
172.1.6.0/24
172.1.7.0/24

Answer: C

Explanation:

Network 172.1.4.0/25 and network 172.1.4.128/25 can be grouped to a single network 172.1.4.0/24

Network 172.1.4.0/24 + Network 172.1.5.0/24 + Network 172.1.6.0/24 + Network 172.1.7.0/24 can be grouped to a single network 172.1.4.0/22 because we have all 4 subnetworks so we can move left 2 bits (2²=4)