Cisco CCNA mock exam questions sample test – Question 366

.Which subnet is IP address 172.16.5.2 /23 a member of, and what is the broadcast address for that subnet?

A. subnet: 172.16.4.0, broadcast: 172.16.5.255
B. subnet: 172.16.5.0, broadcast: 172.16.5.255
C. subnet: 172.16.2.0, broadcast: 172.16.5.255
D. subnet: 172.16.0.0, broadcast: 172.16.7.255

Correct Answer: A

Explanation:
The IP address 172.16.5.2 /23 is a member of subnet 172.16.4.0 and has the broadcast address of 172.16.5.255. The valid host range is between 172.16.4.1 and 172.16.5.254.
Binary form of IP address 172.16.5.2 = 10101100.00010000.00000101.00000010
Binary conversion for /23 netmask = 11111111.11111111.11111110.00000000
Decimal conversion for /23 netmask = 255.255.254.0
Calculations:
Perform the AND operation between the IP address and the netmask to obtain the subnet ID:
Address = 10101100.00010000.00000101.00000010
Netmask = 11111111.11111111.11111110.00000000
——————————————————————————-
Subnetwork ID = 10101100.00010000.00000100.00000000
Convert the binary version of the network ID to dotted decimal format, 172.16.4.0.
To obtain the broadcast address, replace the last 9 host bits (32 – 23 = 9 bits) of the network address, which yields the following:
Binary form of broadcast address = 10101100.00011001.00000101.11111111
Decimal form of broadcast address = 172.16.5.255
Objective:
Network Fundamentals
Sub-Objective:
Apply troubleshooting methodologies to resolve problems
References:
Cisco > Technology Support > IP > IP Routing > Design TechNotes > IP Addressing and Subnetting for New Users > Document ID: 13788 > Understanding IP Addresses
Cisco > Technology Support > IP > IP Addressing Services > Design TechNotes > Subnet Zero and the All-Ones Subnet > Document ID: 13711