The correct statements are that an ARP request is sent as a broadcast to the MAC address FF:FF:FF:FF:FF:FF, and the ARP reply is sent directly as a unicast to the requesting host’s MAC address. This is because ARP operation relies on a two-step process: the request must reach every host on the local segment to find the owner of a target IP, so it uses a Layer 2 broadcast; the reply, however, is unicast because the requesting host’s MAC address is already known from the source hardware address field in the request. On the JNCIA-Junos exam, this concept tests your understanding of how Junos handles Layer 2 address resolution, often appearing in questions that distinguish broadcast from unicast frames. A common trap is assuming the reply is also broadcast—remember that only the request is broadcast, while the reply is a direct unicast. Memory tip: “Request roams, reply returns directly.”
JNCIA-JUNOS Networking Fundamentals Practice Question
This JNCIA-JUNOS practice question tests your understanding of networking fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 about ARP are correct? (Select two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ARP request is sent to the broadcast MAC address
Option A is correct because an ARP request is sent as a broadcast frame to the destination MAC address FF:FF:FF:FF:FF:FF, ensuring all hosts on the local network segment receive it. This allows the host with the target IP address to respond. Option E is correct because the ARP reply is unicast directly to the requesting host's MAC address, which was learned from the source hardware address field in the ARP request.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
ARP request is sent to the broadcast MAC address
Why this is correct
ARP requests are broadcast to all hosts in the subnet.
Related concept
Read the scenario before looking for a memorised answer.
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse ARP with IPv6 Neighbor Discovery, mistakenly thinking ARP works for both IPv4 and IPv6, or they assume ARP replies are broadcast because ARP requests are broadcast.
Detailed technical explanation
How to think about this question
Under the hood, an ARP request contains the sender's hardware and protocol addresses and the target protocol address, with the target hardware address set to zeros. The receiving host updates its ARP cache with the sender's information before sending a unicast reply. In real-world scenarios, gratuitous ARP is used for duplicate IP detection and to update other hosts' ARP caches after a MAC address change, which can cause issues if not handled correctly.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking Fundamentals — This question tests Networking Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ARP request is sent to the broadcast MAC address — Option A is correct because an ARP request is sent as a broadcast frame to the destination MAC address FF:FF:FF:FF:FF:FF, ensuring all hosts on the local network segment receive it. This allows the host with the target IP address to respond. Option E is correct because the ARP reply is unicast directly to the requesting host's MAC address, which was learned from the source hardware address field in the ARP request.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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