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Difficulty: MediumIPv4 Addressing and Subnetting

A network engineer is configuring an interface on a gateway router for an isolated security camera subnet with the network IP address block 192.168.88.192/27192.168.88.192/27. What is the last usable host IP address that can be assigned to a device on this subnet?

  1. 192.168.88.222Answer
  2. B
    192.168.88.223
  3. C
    192.168.88.224
  4. D
    192.168.88.254

Answer

192.168.88.222
For the IPv4 subnet block 192.168.88.192/27192.168.88.192/27, a block size of 32 addresses spans from 192.168.88.192 to 192.168.88.223. The network ID is 192.168.88.192 and the broadcast address is 192.168.88.223. Consequently, the assignable host range is 192.168.88.193 through 192.168.88.222, making 192.168.88.222 the last usable host IP address.

Step-by-Step Solution

1
Determine the block size for a /27 subnet mask.
A /27 prefix leaves 5 host bits (32−27=532 - 27 = 5). The total address count per block is 25=322^5 = 32.
Calculating the block size establishes the address boundary for the subnet.
2
Identify the broadcast address for the subnet block starting at 192.168.88.192.
Adding the block size of 32 to the network ID gives 192+32=224192 + 32 = 224 (the start of the next subnet). Thus, the broadcast address for this block is 192.168.88.223.
The last IP address in any subnet block is reserved for broadcast traffic.
3
Calculate the last usable host IP address.
Subtracting 1 from the broadcast address (192.168.88.223−1192.168.88.223 - 1) yields 192.168.88.222.
Usable host addresses exist strictly between the network ID and the broadcast address.

Key Concept

Subnet Host Boundaries and Usable IP Allocation
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Topics

IPv4 Addressing and Subnetting

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