The router interface with IPv4 address 192.168.10.250 acts as the default gateway for both Web Server 2 and Host 1 on the same LAN. What is the correct subnet mask for this network?

Introduction / Context:
Subnet masks define how host IP addresses are grouped into networks and broadcast domains. When multiple devices share the same default gateway on a simple LAN, they must be in the same IP subnet as the router interface. Choosing the correct subnet mask ensures that hosts correctly identify which addresses are local and which must be forwarded to the gateway.

Given Data / Assumptions:

• Router interface address: 192.168.10.250.
• Web Server 2 and Host 1 use this address as their default gateway.
• All three devices are on the same physical LAN segment.
• We want a typical small office configuration without unusually small subnets.

Concept / Approach:
The address 192.168.10.250 is in a private Class C range. The most common subnet mask for such a network is 255.255.255.0, which yields 256 addresses (including network and broadcast). This mask allows host addresses from 192.168.10.1 through 192.168.10.254, so 192.168.10.250, Web Server 2, and Host 1 can all reside on the same subnet and share the same default gateway. More restrictive masks, such as 255.255.255.192 or 255.255.255.252, would divide the network into smaller ranges and could place the hosts and gateway into incompatible subnets if not carefully designed.

Step-by-Step Solution:
1. Recognize that 192.168.10.250 is a typical gateway address near the top of the usable host range.2. With mask 255.255.255.0, the network is 192.168.10.0 and the broadcast address is 192.168.10.255.3. Valid host addresses in this subnet range from 192.168.10.1 to 192.168.10.254.4. Using this mask, both Web Server 2 and Host 1 can have 192.168.10.x addresses with 192.168.10.250 as their gateway.5. Therefore, 255.255.255.0 is the correct subnet mask for this simple LAN.

Verification / Alternative check:
To verify, you can compute the subnet boundaries for each candidate mask. For example, with 255.255.255.192, the block size in the last octet is 64, so the subnets are 192.168.10.0, .64, .128, and .192. The address 192.168.10.250 falls in the .192 subnet range, which only has host addresses .193 through .254. If hosts are not consistently assigned within the same range, they may not share the gateway correctly. The mask 255.255.255.0 avoids this complication and matches the usual design for such scenarios.

Why Other Options Are Wrong:
Option B, 255.255.255.192, creates smaller subnets and may separate hosts unnaturally. Option C, 255.255.255.250, is not a valid contiguous subnet mask. Option D, 255.255.255.252, allows only two usable host addresses, which is too small for one gateway and multiple hosts on a typical LAN.

Common Pitfalls:
Learners sometimes pick masks based only on the numeric pattern without checking whether all devices fall inside the same subnet. Another pitfall is misunderstanding valid subnet masks and proposing values that do not correspond to contiguous one bits followed by zeros in binary.

Final Answer:
255.255.255.0