Examkin

Question

Difficulty: HardIPv4 Addressing and Subnetting

A network engineer is provisioning subnets from the parent address block 192.168.64.0/20192.168.64.0/20 for a newly constructed facility. The primary VLAN requires capacity for at least 100100 usable host IP addresses while minimizing wasted address space. If the engineer allocates the first available valid subnet from this block that satisfies the host capacity requirement, what is the broadcast address of this allocated subnet?

  1. 192.168.64.127192.168.64.127Answer
  2. B
    192.168.64.126192.168.64.126
  3. C
    192.168.64.255192.168.64.255
  4. D
    192.168.64.63192.168.64.63

Answer

The broadcast address of the allocated subnet is 192.168.64.127192.168.64.127.
To host at least 100 devices with minimal address waste, 7 host bits are required (27−2=1262^7 - 2 = 126 usable hosts), which corresponds to a /25/25 subnet mask. The first /25/25 subnet within 192.168.64.0/20192.168.64.0/20 occupies the IP block 192.168.64.0192.168.64.0 to 192.168.64.127192.168.64.127. The final address of this block, 192.168.64.127192.168.64.127, serves as the broadcast address.

Step-by-Step Solution

1
Determine the minimum prefix length needed for 100 usable hosts.
Prefix length /25/25 (7 host bits, providing 27−2=1262^7 - 2 = 126 usable hosts).
A /26/26 prefix only offers 26−2=622^6 - 2 = 62 usable host addresses, which is insufficient. A /25/25 prefix provides 126126 usable addresses, satisfying the requirement of at least 100 hosts while minimizing wasted space.
2
Identify the network boundary of the first /25/25 subnet inside the 192.168.64.0/20192.168.64.0/20 parent block.
Network ID: 192.168.64.0/25192.168.64.0/25.
Subnetting starts sequentially from the lowest network ID of the parent block.
3
Calculate the broadcast address of the 192.168.64.0/25192.168.64.0/25 subnet.
Broadcast Address: 192.168.64.127192.168.64.127.
With a block size of 128128 IP addresses (272^7), the subnet range spans 192.168.64.0192.168.64.0 through 192.168.64.127192.168.64.127. The last IP address in the block is reserved for broadcast.

Key Concept

Subnet Masking and Broadcast Address Calculation
Rate this question

Topics

IPv4 Addressing and Subnetting

More questions from this topic