Question 270 of 464
RFC 1918 Private IP Address Ranges: Class A, B, and C
A network engineer is reviewing RFC 1918 address ranges to plan a private IP addressing scheme. Which of the following IP addresses falls within the private address space for Class A?
Quick Answer
The correct answer is 10.10.10.1, as it falls within the RFC 1918 private IP address range for Class A, which is defined as 10.0.0.0/8. This means any address from 10.0.0.0 through 10.255.255.255 is reserved exclusively for internal network use and is not routable on the public internet. On the CompTIA Network+ N10-009 exam, you will often see questions that test your ability to distinguish these private ranges from public or link-local addresses, with a common trap being addresses like 172.16.0.1 or 192.168.1.1 that belong to Class B and C ranges respectively. To lock in the Class A range, remember the mnemonic “10 is the one” — only the 10.x.x.x block uses the /8 prefix, giving you over 16 million private hosts.
⚠ Common exam trap
Many candidates confuse the Class B private range (172.16.0.0/12) with any 172.x.x.x address, forgetting that only 172.16.0.0 through 172.31.255.255 are private, while 172.32.0.0 and above are public.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
10.10.10.1
RFC 1918 defines the Class A private address range as 10.0.0.0/8, which includes all addresses from 10.0.0.0 to 10.255.255.255. 10.10.10.1 falls within this range, making it a valid private IP address for internal network use.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
172.16.0.1
Why it's wrong here
172.16.0.1 is in the Class B private range (172.16.0.0/12), not Class A.
When this WOULD be correct
This option would be correct if the question asked for a private IP address within the Class B range, or if it asked for an address in the 172.16.0.0/12 block without specifying class.
- ✗
192.168.1.1
Why it's wrong here
192.168.1.1 is in the Class C private range (192.168.0.0/16), not Class A.
When this WOULD be correct
This option would be correct if the question asked: 'Which of the following IP addresses falls within the private address space for Class C?' or 'Which address is in the 192.168.0.0/16 range?'
- ✓
10.10.10.1
Why this is correct
10.10.10.1 falls within the 10.0.0.0/8 block, which is the Class A private address space defined in RFC 1918.
- ✗
172.32.0.1
Why it's wrong here
172.32.0.1 is not within the 172.16.0.0/12 private block; it falls outside the private range.
When this WOULD be correct
If the question asked for a public IP address or an address in the 172.32.0.0/16 range (which is public), then 172.32.0.1 could be correct. For example, 'Which of the following is a public IP address?'
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓10.10.10.1Correct answer▾
Why this is correct
10.10.10.1 falls within the 10.0.0.0/8 block, which is the Class A private address space defined in RFC 1918.
✗172.16.0.1Wrong answer — click to see why▾
Why this is wrong here
The 172.16.0.1 address is part of the Class B private range (172.16.0.0/12), not Class A. The question specifically asks for a Class A private address, which is 10.0.0.0/8.
★ When this WOULD be the correct answer
This option would be correct if the question asked for a private IP address within the Class B range, or if it asked for an address in the 172.16.0.0/12 block without specifying class.
Why candidates choose this
Candidates may confuse the Class B private range (172.16.0.0/12) with Class A because 172.x.x.x addresses are commonly used in private networks, leading them to overlook the specific class designation.
✗192.168.1.1Wrong answer — click to see why▾
Why this is wrong here
The question asks for a Class A private address per RFC 1918. 192.168.1.1 is a Class C private address (192.168.0.0/16), not Class A.
★ When this WOULD be the correct answer
This option would be correct if the question asked: 'Which of the following IP addresses falls within the private address space for Class C?' or 'Which address is in the 192.168.0.0/16 range?'
Why candidates choose this
Candidates often confuse the private ranges or think any private address qualifies, not realizing the question specifies Class A.
✗172.32.0.1Wrong answer — click to see why▾
Why this is wrong here
172.32.0.1 is not within the RFC 1918 private address ranges; the Class B private range is 172.16.0.0/12 (172.16.0.0 to 172.31.255.255), and 172.32.0.1 falls outside that range.
★ When this WOULD be the correct answer
If the question asked for a public IP address or an address in the 172.32.0.0/16 range (which is public), then 172.32.0.1 could be correct. For example, 'Which of the following is a public IP address?'
Why candidates choose this
Candidates often mistakenly think that any address starting with 172 is private, not realizing that only 172.16.0.0/12 is reserved, and addresses like 172.32.0.0/16 are public.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
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Same concept, more angles
1 more way this is tested on N10-009
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which of the following IP addresses is a private IP address as defined by RFC 1918?
easy- A.169.254.1.1
- B.172.32.1.1
- ✓ C.192.168.1.1
- D.172.15.1.1
Why C: (192.168.1.1) is correct because RFC 1918 reserves the 192.168.0.0/16 block (192.168.0.0 – 192.168.255.255) for private use within local networks. This address is not routable on the public internet, making it suitable for internal LAN addressing.
Last reviewed: Jun 11, 2026
This N10-009 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the N10-009 exam.
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