JN0-106 Networking Fundamentals Practice Question
Which TWO statements about ARP are correct? (Select two.)
⚠ Common exam trap
Many candidates 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.
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
✓
ARP request is sent to the broadcast MAC address
Option A is correct because an ARP request must reach every device on the local segment, so it is encapsulated in a frame with the broadcast destination MAC address FF:FF:FF:FF:FF:FF. Option E is correct because the ARP reply is unicast: the responding host already knows the requester's MAC address from the sender hardware address field in the request, so it sends the reply directly to that MAC address. Option B is wrong because ARP requests use the broadcast MAC address, not a multicast address (IPv6 uses multicast with Neighbor Discovery instead of ARP). Option C is wrong because the reply is unicast to the requester, not broadcast, which would waste bandwidth and force all hosts to process it. Option D is wrong because ARP resolves IPv4 addresses to MAC addresses; IPv6 uses Neighbor Discovery (NDP) with ICMPv6 rather than ARP.
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 Layer 2 broadcast frames sent to FF:FF:FF:FF:FF:FF. Because the sender does not know the target's MAC address, it must reach every host on the local subnet simultaneously, prompting only the node that owns the target IPv4 address to respond. This broadcast mechanism is fundamental to how ARP resolves IPv4 addresses to MAC addresses on a LAN.
- ✗
ARP request is sent to a multicast MAC address
Why it's wrong here
ARP does not use multicast for its requests. Layer 2 multicast MAC addresses (e.g., 01:00:5E:...) are utilized by protocols such as IGMP or IPv6 Neighbor Discovery, but IPv4 ARP specifically uses the broadcast address. Furthermore, multicast would require a defined group membership, which does not exist for the purpose of address resolution in IPv4.
- ✗
ARP reply is sent to the broadcast MAC address
Why it's wrong here
If ARP replies were sent to the broadcast address, every host on the subnet would be forced to process and discard the frame, wasting bandwidth and CPU cycles. The replying host already knows the requester's MAC address from the source address field of the ARP request, so it can send a unicast reply directly. Broadcasting replies would violate the efficiency design of ARP and introduce unnecessary network overhead.
- ✗
ARP is used for both IPv4 and IPv6
Why it's wrong here
ARP is strictly an IPv4 protocol; IPv6 uses Neighbor Discovery Protocol (NDP) instead. NDP relies on ICMPv6 messages and solicited-node multicast addresses to perform address resolution and also handles tasks like duplicate address detection and router discovery, which ARP does not. Thus saying ARP is used for both IPv4 and IPv6 is incorrect.
- ✓
ARP reply is sent directly to the requesting host's MAC address
Why this is correct
The ARP reply is a unicast frame addressed to the MAC address of the host that sent the original request, which is recorded in the request's Ethernet source address. The replying host includes its own MAC and IP address so the requester can update its ARP cache with the resolved mapping. This direct unicast reply confines the response to exactly one node, minimizing unnecessary traffic on the local network.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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