- A
Private IPv4 addresses are not directly Internet-routable.
This is correct because RFC 1918 private ranges are intended for internal use and are not routed on the public Internet.
- B
Public IPv4 addresses are intended to be globally unique and routable.
This is correct because public IPv4 addresses are used for global Internet reachability.
- C
Private IPv4 addresses always require OSPF to function inside a LAN.
Why wrong: This is wrong because private addresses can be used locally without any requirement for OSPF.
- D
Public IPv4 addresses cannot exist on Internet-facing devices.
Why wrong: This is wrong because Internet-facing devices commonly use public addresses specifically to be reachable across the Internet.
- E
Private and public IPv4 addresses are both automatically translated by ARP.
Why wrong: This is wrong because ARP resolves IP-to-MAC on a local link and does not perform private/public address translation.
Quick Answer
The correct answer is that private IPv4 addresses are not directly Internet-routable, while public IPv4 addresses are globally unique and routable across the Internet. This distinction exists because private IPv4 addresses, defined in RFC 1918 (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16), are reserved for internal use within local networks and are intentionally blocked by Internet routers. Public addresses, by contrast, are assigned by IANA and must be unique worldwide to enable direct end-to-end communication. On the CCNA 200-301 v2 exam, this concept frequently appears in questions about NAT and routing behavior, with a common trap being the assumption that any valid LAN address can reach the Internet without translation. Remember the key rule: private addresses are for internal LANs only; they require NAT to become public. A useful mnemonic is “Private stays inside, public goes worldwide.”
CCNA Network Infrastructure and Connectivity Practice Question
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: private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.. 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.
Which two statements accurately compare IPv4 private addresses and public addresses?
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
Private IPv4 addresses are not directly Internet-routable.
Private IPv4 addresses are intended for internal use and are not directly routable on the public Internet. In plain language, they are designed for use inside organizations, homes, and other local environments without consuming globally unique public space. Public addresses, by contrast, are intended to be unique and routable across the Internet. This is one of the main reasons NAT became so common in IPv4 environments. CCNA questions often test this distinction because learners sometimes confuse “valid inside a LAN” with “routable everywhere.” Private addressing is extremely useful, but it does not eliminate the need for translation or public addressing when reaching the Internet. The two correct statements are the ones that preserve that basic separation between internal-use ranges and globally routable address space.
Key principle: Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Private IPv4 addresses are not directly Internet-routable.
Why this is correct
This is correct because RFC 1918 private ranges are intended for internal use and are not routed on the public Internet.
Related concept
Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
- ✓
Public IPv4 addresses are intended to be globally unique and routable.
Why this is correct
This is correct because public IPv4 addresses are used for global Internet reachability.
Related concept
Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
- ✗
Private IPv4 addresses always require OSPF to function inside a LAN.
Why it's wrong here
This is wrong because private addresses can be used locally without any requirement for OSPF.
When this WOULD be correct
If the question were to ask about the requirements for routing protocols in a specific network setup that exclusively uses OSPF for all internal communications, then this statement could be correct. For example, a scenario where a network design mandates OSPF for all routing, including private addresses, would validate this option.
- ✗
Public IPv4 addresses cannot exist on Internet-facing devices.
Why it's wrong here
This is wrong because Internet-facing devices commonly use public addresses specifically to be reachable across the Internet.
When this WOULD be correct
If the exam question stated that 'Public IPv4 addresses are only used in private networks' or 'Public IPv4 addresses are never assigned to devices that connect directly to the Internet,' then option D would be correct. Such a scenario would misrepresent the nature of public IP addresses.
- ✗
Private and public IPv4 addresses are both automatically translated by ARP.
Why it's wrong here
This is wrong because ARP resolves IP-to-MAC on a local link and does not perform private/public address translation.
When this WOULD be correct
In a question that asks about the functions of ARP in a network where both private and public addressing schemes are in use, one might state that ARP is involved in the translation process, making this option correct in that context.
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 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Private IPv4 addresses are not directly Internet-routable.Correct answer▾
Why this is correct
This is correct because RFC 1918 private ranges are intended for internal use and are not routed on the public Internet.
✗Private IPv4 addresses always require OSPF to function inside a LAN.Wrong answer — click to see why▾
Why this is wrong here
Private IPv4 addresses do not require OSPF or any specific routing protocol to function inside a LAN; they can operate with static routes or any dynamic routing protocol. OSPF is just one option and is not mandatory.
★ When this WOULD be the correct answer
If the question were to ask about the requirements for routing protocols in a specific network setup that exclusively uses OSPF for all internal communications, then this statement could be correct. For example, a scenario where a network design mandates OSPF for all routing, including private addresses, would validate this option.
Why candidates choose this
Students might associate private addresses with internal networks and mistakenly think OSPF is commonly used there, but OSPF is not a requirement for private address operation.
✗Public IPv4 addresses cannot exist on Internet-facing devices.Wrong answer — click to see why▾
Why this is wrong here
Public IPv4 addresses are specifically used on Internet-facing devices to enable global reachability. Without public addresses, devices would not be directly accessible from the Internet.
★ When this WOULD be the correct answer
If the exam question stated that 'Public IPv4 addresses are only used in private networks' or 'Public IPv4 addresses are never assigned to devices that connect directly to the Internet,' then option D would be correct. Such a scenario would misrepresent the nature of public IP addresses.
Why candidates choose this
A student might confuse public addresses with private ones, thinking public addresses are only for internal use, but the opposite is true.
✗Private and public IPv4 addresses are both automatically translated by ARP.Wrong answer — click to see why▾
Why this is wrong here
ARP (Address Resolution Protocol) resolves IP addresses to MAC addresses on a local network segment and does not perform any translation between private and public addresses. NAT (Network Address Translation) handles that translation.
★ When this WOULD be the correct answer
In a question that asks about the functions of ARP in a network where both private and public addressing schemes are in use, one might state that ARP is involved in the translation process, making this option correct in that context.
Why candidates choose this
The acronym 'ARP' might be confused with 'NAT' or 'PAT' by students who are not clear on the functions of each protocol.
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
Common exam trap: answer the scenario, not the keyword
Be careful not to confuse the routability of private addresses with their validity within a LAN. Private addresses need NAT for Internet access.
Detailed technical explanation
How to think about this question
IPv4 addressing is divided into two main categories: private and public addresses. Private IPv4 addresses are defined by RFC 1918 and are reserved for use within private networks such as corporate LANs or home networks. These addresses are not routable on the public Internet, meaning routers on the Internet will not forward packets with private source or destination addresses. Public IPv4 addresses, on the other hand, are globally unique and assigned by Internet registries to ensure that devices using these addresses can communicate across the Internet without address conflicts. The fundamental rule governing private and public IPv4 addresses is their routability and uniqueness. Private addresses are intended solely for internal communication and require Network Address Translation (NAT) to communicate with public networks. Public addresses must be unique worldwide and are directly routable on the Internet. Cisco devices and CCNA exam scenarios often emphasize this distinction because it affects routing, NAT configuration, and security policies. Understanding which addresses are routable and which are not is critical for designing and troubleshooting networks. A common exam trap is confusing private address usability inside a LAN with their ability to be routed on the Internet. Many learners assume private addresses can be used anywhere without restriction, but they must be translated to public addresses for Internet access. Cisco devices use NAT to translate private addresses to public ones, enabling communication beyond the local network. Recognizing this separation helps avoid misconfigurations and clarifies why public addresses are necessary for Internet-facing interfaces.
KKey Concepts to Remember
- Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
- Public IPv4 addresses are globally unique and designed to be routable across the Internet without requiring translation.
- Network Address Translation (NAT) is required to allow devices with private IPv4 addresses to communicate with public Internet hosts.
- Cisco routers do not forward packets with private source or destination addresses across public Internet links by default.
- Private IPv4 address ranges are defined by RFC 1918 and include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16.
- Public IPv4 addresses are assigned by Internet registries to ensure uniqueness and prevent routing conflicts globally.
- Private IPv4 addresses can be used freely inside LANs without routing protocols like OSPF, as they do not require Internet routing.
- Understanding the difference between private and public IPv4 addresses is essential for configuring NAT and designing secure network architectures.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts..
What is the correct answer to this question?
The correct answer is: Private IPv4 addresses are not directly Internet-routable. — Private IPv4 addresses are intended for internal use and are not directly routable on the public Internet. In plain language, they are designed for use inside organizations, homes, and other local environments without consuming globally unique public space. Public addresses, by contrast, are intended to be unique and routable across the Internet. This is one of the main reasons NAT became so common in IPv4 environments. CCNA questions often test this distinction because learners sometimes confuse “valid inside a LAN” with “routable everywhere.” Private addressing is extremely useful, but it does not eliminate the need for translation or public addressing when reaching the Internet. The two correct statements are the ones that preserve that basic separation between internal-use ranges and globally routable address space.
What should I do if I get this 200-301 question wrong?
Review private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Private IPv4 addresses are reserved for internal network use and are not routable on the public Internet to prevent address conflicts.
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Last reviewed: May 17, 2026
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