Examkin

Question

Difficulty: MediumIPv4 Addressing and Subnetting

A network administrator is assigning an IP address to a newly installed interface on a database server. The server is configured with the IP address 172.28.140.197172.28.140.197 and a subnet mask of 255.255.252.0255.255.252.0. Which IPv4 address represents the subnet broadcast address for this server's subnetwork?

  1. 172.28.143.255172.28.143.255Answer
  2. B
    172.28.140.255172.28.140.255
  3. C
    172.28.143.254172.28.143.254
  4. D
    172.32.143.255172.32.143.255

Answer

172.28.143.255172.28.143.255
For the IP address 172.28.140.197172.28.140.197 with subnet mask 255.255.252.0255.255.252.0 (/22), the third octet operates in increments of 44 (256−252=4256 - 252 = 4). Since 140140 is a multiple of 44, the subnetwork begins at 172.28.140.0172.28.140.0 and extends up to 172.28.143.255172.28.143.255. Therefore, the address 172.28.143.255172.28.143.255 is the broadcast address for this subnetwork.

Step-by-Step Solution

1
Convert the dotted-decimal subnet mask to CIDR notation and identify the interesting octet.
The subnet mask 255.255.252.0255.255.252.0 corresponds to a /22/22 prefix (8+8+6+0=228 + 8 + 6 + 0 = 22 bits). The interesting octet is the third octet.
Determining the prefix length isolates which octet controls the subnetwork boundaries.
2
Calculate the subnetwork block size for the third octet.
Block size =256−252=4= 256 - 252 = 4.
The block size specifies the interval at which subnetwork addresses increment in the third octet.
3
Find the network address containing the host IP address 172.28.140.197172.28.140.197.
Dividing 140140 by 44 gives exactly 3535 with no remainder. Thus, the network ID is 172.28.140.0172.28.140.0.
The network address is the starting boundary of the subnet block.
4
Determine the broadcast address by adding (block size - 1) to the third octet and setting all host bits in the fourth octet to 1s (255255).
Third octet upper bound =140+4−1=143= 140 + 4 - 1 = 143. Broadcast address =172.28.143.255= 172.28.143.255.
The broadcast address is the last IP address in the subnetwork range.

Key Concept

IPv4 Subnet Mask Evaluation and Broadcast Address Calculation
Rate this question

Topics

IPv4 Addressing and Subnetting

More questions from this topic