Quick Answer
The correct answer is 172.20.0.0/16 because it falls within the RFC 1918 private IPv4 address range of 172.16.0.0/12, which is reserved for internal use and cannot be routed on the public Internet. RFC 1918 defines three private blocks: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, all designed for unrestricted internal routing while being filtered by public routers. On the CCNA 200-301 v2 exam, this concept tests your ability to distinguish private from public, link-local, and reserved addresses—a common trap is confusing the 172.16.0.0/12 range (which includes 172.16.0.0 through 172.31.255.255) with public 172.x.x.x addresses outside that block. Remember the mnemonic “10, 172, 192” for the first octets, and for the 172 range, think “16 to 31” as the second octet range to avoid picking a public address.
This 200-301 practice question tests your understanding of network infrastructure and connectivity. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: rFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company wants private IPv4 addressing that can be routed internally but not on the public Internet. Which range meets that requirement?
198.51.100.0/24
Why wrong: This is a documentation range, not an RFC 1918 private range.
172.20.0.0/16
Correct. It falls within the private 172.16.0.0/12 block.
169.254.0.0/16
Why wrong: That is link-local APIPA space, not general private addressing for routed design.
224.0.0.0/4
Why wrong: That is multicast space.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
172.20.0.0/16
RFC 1918 defines private IPv4 ranges for internal routing: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. 172.20.0.0/16 falls within the 172.16.0.0/12 block, making it a valid private address. 198.51.100.0/24 is reserved for documentation (TEST-NET-2) and should not be used internally. 169.254.0.0/16 is link-local (APIPA), used only for automatic addressing on a single link. 224.0.0.0/4 is multicast, not routable as unicast and not private.
Key principle: RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
198.51.100.0/24
Why it's wrong here
This is a documentation range, not an RFC 1918 private range.
When this WOULD be correct
If the question asked for an IP range that is suitable for documentation or examples in network design, then 198.51.100.0/24 would be correct, as it is specifically designated for such purposes.
172.20.0.0/16
Why this is correct
Correct. It falls within the private 172.16.0.0/12 block.
Related concept
RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet.
169.254.0.0/16
Why it's wrong here
That is link-local APIPA space, not general private addressing for routed design.
When this WOULD be correct
In a question asking for a range suitable for automatic IP address assignment in a local network without a DHCP server, 169.254.0.0/16 would be the correct answer. This scenario would focus on local connectivity rather than internal routing.
224.0.0.0/4
Why it's wrong here
That is multicast space.
When this WOULD be correct
In a question asking for the range of IP addresses designated for multicast traffic within a private network, option D would be correct. For example, if the question specified the need for a range that supports multicast applications internally without public routing, then this option would be valid.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is correct
Correct. It falls within the private 172.16.0.0/12 block.
Why this is wrong here
Option A (198.51.100.0/24) is wrong because it falls within the range of documentation-only IP addresses, which are not intended for private use and can be routed on the public Internet.
★ When this WOULD be the correct answer
If the question asked for an IP range that is suitable for documentation or examples in network design, then 198.51.100.0/24 would be correct, as it is specifically designated for such purposes.
Why candidates choose this
Candidates might choose this option due to familiarity with the 198.51.100.0/24 range being used in examples and documentation, leading them to mistakenly associate it with private addressing.
Why this is wrong here
The 169.254.0.0/16 range is designated for link-local addresses, which are used for automatic IP address assignment in the absence of a DHCP server. These addresses cannot be routed beyond the local network segment, making them unsuitable for internal routing requirements.
★ When this WOULD be the correct answer
In a question asking for a range suitable for automatic IP address assignment in a local network without a DHCP server, 169.254.0.0/16 would be the correct answer. This scenario would focus on local connectivity rather than internal routing.
Why candidates choose this
Candidates may choose this option due to familiarity with the 169.254.0.0 range as a private addressing scheme, mistakenly associating it with internal networking without recognizing its limitations in routing.
Why this is wrong here
Option D, 224.0.0.0/4, is incorrect because it is part of the multicast address range, which is used for one-to-many communication and not suitable for private addressing that is routable internally.
★ When this WOULD be the correct answer
In a question asking for the range of IP addresses designated for multicast traffic within a private network, option D would be correct. For example, if the question specified the need for a range that supports multicast applications internally without public routing, then this option would be valid.
Why candidates choose this
Candidates might be tempted to choose this option due to a misunderstanding of IP address classes, confusing multicast addresses with private addressing, especially if they are familiar with the concept of internal communication.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Be careful not to confuse reserved IP ranges for documentation or link-local use with private IP ranges.
Detailed technical explanation
Private IPv4 addressing is defined by RFC 1918 to provide IP address ranges that organizations can use internally without conflicting with public Internet addresses. These private addresses are routable within an organization's internal network but are not routable on the public Internet, ensuring internal communication while preserving global address uniqueness. The three main private IPv4 blocks are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, each offering different address space sizes for various network scales. The decision to select 172.20.0.0/16 as a private address range follows the rule that any IP within 172.16.0.0 to 172.31.255.255 is reserved for private use. This range is part of the 172.16.0.0/12 block, which includes addresses from 172.16.0.0 to 172.31.255.255. Cisco devices and routing protocols recognize these addresses as private, allowing internal routing without leaking to the public Internet. Using this range enables internal routing protocols like OSPF or EIGRP to operate normally without IP conflicts. A common exam trap is confusing private address ranges with other special-use IP blocks such as link-local (169.254.0.0/16), multicast (224.0.0.0/4), or documentation/test ranges (198.51.100.0/24). These are not suitable for internal routing or private addressing. For example, 169.254.0.0/16 is used for Automatic Private IP Addressing (APIPA) and is not routable. Understanding these distinctions helps avoid selecting incorrect ranges that would break internal routing or cause addressing conflicts.
Key takeaway
RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet.
Real-world example
A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Review rFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet..
The correct answer is: 172.20.0.0/16 — RFC 1918 defines private IPv4 ranges for internal routing: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. 172.20.0.0/16 falls within the 172.16.0.0/12 block, making it a valid private address. 198.51.100.0/24 is reserved for documentation (TEST-NET-2) and should not be used internally. 169.254.0.0/16 is link-local (APIPA), used only for automatic addressing on a single link. 224.0.0.0/4 is multicast, not routable as unicast and not private.
Review rFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet., then practise related 200-301 questions on the same topic to reinforce the concept.
RFC 1918 defines three private IPv4 address blocks that are routable internally but not on the public Internet.
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Last reviewed: May 17, 2026
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