CERTIFIED-IN-CYBERSECURITY · Question #778
CERTIFIED-IN-CYBERSECURITY Question #778: Real Exam Question with Answer & Explanation
The correct answer is D: /27. A subnet mask is a number that distinguishes between the network address and the host address. Subnetting divides a network into two or more subnets (see ISC2 Study Guide, chapter 4, module 1). To allow 30 hosts + 2 addresses for broadcast and network addresses. Thus, we are look
Question
Which of these different sub-masks will allow 30 hosts? ()
Options
- A/26
- B/29
- C/30
- D/27
Explanation
A subnet mask is a number that distinguishes between the network address and the host address. Subnetting divides a network into two or more subnets (see ISC2 Study Guide, chapter 4, module 1). To allow 30 hosts + 2 addresses for broadcast and network addresses. Thus, we are looking for the mask 255.255.255.224, or /27 using CIDR (Classless Inter-Domain Routing) notation. For 32 addresses, we need 5 bits and the mask /32 - log2(32) = /32 - 5 = /27. As for the remaining masks, /26 would result in 64 hosts, /29 in 8 hosts, and /30 in 4 hosts.
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