Given the base network address 192.168.10.0/24, perform Variable Length Subnet Masking (VLSM) to accommodate the following host requirements…

Given the base network address 192.168.10.0/24, perform Variable Length Subnet Masking (VLSM) to accommodate the following host requirements. Determine the network address and subnet mask for each subnet.

SubnetRequired Hosts
A25
B22
C8
D2
E2

From the BPDB Assistant Engineer (CSE) October 2026 – Written (BUET) exam, question 22 of 30.

Answers (1)

VLSM: serve the largest requirement first, each from the smallest block that fits (block size = 2^host bits, usable = block − 2).

A — 25 hosts → needs 32 addresses (30 usable): /27

  • Network 192.168.10.0/27, mask 255.255.255.224
  • Usable 192.168.10.1 – .30, broadcast .31

B — 22 hosts → /27 (30 usable)

  • Network 192.168.10.32/27, mask 255.255.255.224
  • Usable 192.168.10.33 – .62, broadcast .63

C — 8 hosts → a /29 gives only 6 usable, so /28 (14 usable)

  • Network 192.168.10.64/28, mask 255.255.255.240
  • Usable 192.168.10.65 – .78, broadcast .79

D — 2 hosts → /30 (2 usable)

  • Network 192.168.10.80/30, mask 255.255.255.252
  • Usable 192.168.10.81 – .82, broadcast .83

E — 2 hosts → /30

  • Network 192.168.10.84/30, mask 255.255.255.252
  • Usable 192.168.10.85 – .86, broadcast .87

192.168.10.88 – 192.168.10.255 is left free for future subnets.

— rhs

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