A security administrator is creating a new firewall object for a device with IP address 192.168.100.1/25. However, the firewall software only uses dotted decimal notation in configuration fields…

The correct answer is C. 255.255.255.128. A /25 subnet mask means 25 bits are reserved for the network portion, leaving 7 bits for host addresses. In dotted decimal, that is: 11111111.11111111.11111111.10000000 Decimal equivalent: 255.255.255.128

Submitted by omar99· Mar 6, 2026Network implementation

Question

A security administrator is creating a new firewall object for a device with IP address 192.168.100.1/25. However, the firewall software only uses dotted decimal notation in configuration fields. Which of the following is the correct subnet mask to use?

Options

A255.255.254.0
B255.255.255.1
C255.255.255.128
D255.255.255.192

How the community answered

(38 responses)

A
3% (1)
B
8% (3)
C
76% (29)
D
13% (5)

Explanation

A /25 subnet mask means 25 bits are reserved for the network portion, leaving 7 bits for host addresses. In dotted decimal, that is: 11111111.11111111.11111111.10000000 Decimal equivalent: 255.255.255.128

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