CV0-003 · Question #175
A technician needs to configure a virtual NIC on a Class A IP address network. Which of the following is the default subnet mask for this network?
The correct answer is A. /8. Class A IP addresses (1.0.0.0 to 126.255.255.255) use a default subnet mask of 255.0.0.0, which equals a /8 prefix length in CIDR notation.
Question
A technician needs to configure a virtual NIC on a Class A IP address network. Which of the following is the default subnet mask for this network?
Options
- A/8
- B/16
- C/24
- D/28
How the community answered
(43 responses)- A91% (39)
- B2% (1)
- C2% (1)
- D5% (2)
Why each option
Class A IP addresses (1.0.0.0 to 126.255.255.255) use a default subnet mask of 255.0.0.0, which equals a /8 prefix length in CIDR notation.
In classful IP addressing, a Class A network uses only the first octet for the network portion and the remaining three octets for hosts, giving a default mask of 255.0.0.0. In CIDR notation this is /8, meaning 8 bits are masked. This allows for up to 16,777,214 hosts per Class A network.
/16 (255.255.0.0) is the default subnet mask for Class B networks, which span 128.0.0.0 to 191.255.255.255.
/24 (255.255.255.0) is the default subnet mask for Class C networks, which span 192.0.0.0 to 223.255.255.255.
/28 (255.255.255.240) is a custom subnet used for very small networks with 14 usable host addresses and is not a default classful mask.
Concept tested: Classful IP addressing and Class A default subnet mask
Source: https://learn.microsoft.com/en-us/troubleshoot/windows-client/networking/default-subnet-mask-ip-address-classes
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