Quick Answer
The answer is Neighbor Discovery (ND). IPv6 replaces the Address Resolution Protocol (ARP) used in IPv4 with the Neighbor Discovery Protocol because ARP was a separate, broadcast-based protocol that lacked security and efficiency, whereas ND operates over ICMPv6 using multicast messages to perform address resolution, router discovery, and duplicate address detection as integrated functions. On the CCNA 200-301 v2 exam, this concept tests your understanding of how IPv6 handles local-link communication differently from IPv4; a common trap is confusing ND with ARP or assuming IPv6 still uses broadcasts. Remember that IPv6 has no broadcasts—ND uses solicited-node multicast instead. A helpful memory tip: think of ND as the "neighborly" replacement that does everything ARP did, but better and more securely, using ICMPv6 messages like Neighbor Solicitation and Neighbor Advertisement.
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: neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages.. 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 IPv6 protocol function replaces ARP?
DHCPv6
Why wrong: DHCPv6 provides addressing information, not local-link address resolution by itself.
Neighbor Discovery
Correct. Neighbor Discovery replaces ARP in IPv6 networks.
EUI-64
Why wrong: EUI-64 is one method of generating an interface identifier, not an address resolution protocol.
SLAAC
Why wrong: SLAAC is an addressing method, not the ARP replacement mechanism.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Neighbor Discovery
IPv6 uses Neighbor Discovery Protocol to resolve Layer 3-to-Layer 2 information and perform related local-link functions such as router discovery and address resolution.
Key principle: Neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DHCPv6
Why it's wrong here
DHCPv6 provides addressing information, not local-link address resolution by itself.
When this WOULD be correct
If the exam question asked about protocols involved in IPv6 address assignment or configuration, such as 'Which protocol is responsible for dynamically assigning IPv6 addresses to devices?', then DHCPv6 would be the correct answer.
Neighbor Discovery
EUI-64
Why it's wrong here
EUI-64 is one method of generating an interface identifier, not an address resolution protocol.
When this WOULD be correct
If the exam question asked about methods for generating IPv6 addresses or identifiers, specifically in the context of creating unique addresses from MAC addresses, then EUI-64 would be the correct answer.
SLAAC
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. Neighbor Discovery replaces ARP in IPv6 networks.
Why this is wrong here
DHCPv6 is not a protocol that replaces ARP; instead, it is used for assigning IP addresses and configuration information to IPv6 devices. ARP is replaced by the Neighbor Discovery Protocol in IPv6, which performs similar functions for address resolution.
★ When this WOULD be the correct answer
If the exam question asked about protocols involved in IPv6 address assignment or configuration, such as 'Which protocol is responsible for dynamically assigning IPv6 addresses to devices?', then DHCPv6 would be the correct answer.
Why candidates choose this
Candidates may find DHCPv6 tempting because it is a well-known protocol associated with IP address management, leading them to mistakenly associate it with the address resolution functions that ARP performed in IPv4.
Why this is wrong here
EUI-64 is not a protocol but a method for generating IPv6 interface identifiers. It does not perform the function of resolving link-layer addresses like ARP does in IPv4.
★ When this WOULD be the correct answer
If the exam question asked about methods for generating IPv6 addresses or identifiers, specifically in the context of creating unique addresses from MAC addresses, then EUI-64 would be the correct answer.
Why candidates choose this
Candidates may confuse EUI-64 with address resolution functions due to its association with IPv6 addressing, leading them to mistakenly believe it plays a role similar to ARP.
Why this is wrong here
SLAAC (Stateless Address Autoconfiguration) is a method for automatically configuring IPv6 addresses but does not perform the function of resolving link-layer addresses like ARP does in IPv4. Therefore, it cannot replace ARP in IPv6.
★ When this WOULD be the correct answer
If the exam question asked which protocol is responsible for automatically configuring IPv6 addresses without requiring a DHCP server, then SLAAC would be the correct answer. This would focus on address assignment rather than address resolution.
Why candidates choose this
Candidates might choose SLAAC because it is associated with IPv6 address configuration, leading to confusion between address assignment and address resolution functions, making it seem relevant to the question.
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 protocols that manage IP addresses or routing with those that resolve addresses.
Detailed technical explanation
Neighbor Discovery Protocol (NDP) is a fundamental IPv6 protocol that replaces ARP by resolving IPv6 addresses to MAC addresses on a local network segment. NDP uses ICMPv6 messages to perform address resolution, router discovery, prefix discovery, and duplicate address detection. This protocol is integral to IPv6 because it consolidates multiple functions that were handled by separate protocols in IPv4, streamlining network operations. In Cisco and CCNA contexts, NDP operates by sending Neighbor Solicitation messages to determine the link-layer address of a target IPv6 address. When a device receives this solicitation, it replies with a Neighbor Advertisement containing its MAC address. This process ensures efficient Layer 3 to Layer 2 mapping. Additionally, NDP supports Stateless Address Autoconfiguration (SLAAC) by advertising network prefixes and default routers, which DHCPv6 does not replace. A common exam trap is confusing DHCPv6 or SLAAC with the ARP replacement function. While DHCPv6 provides IP address assignment and SLAAC enables automatic address configuration, neither performs address resolution. Understanding that NDP uniquely handles address resolution and local-link discovery in IPv6 networks is critical to avoid this mistake. Practically, Cisco devices rely on NDP for neighbor reachability and efficient packet forwarding on IPv6 networks.
Key takeaway
Neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages.
Real-world example
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
Review neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages., 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 — Neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages..
The correct answer is: Neighbor Discovery — IPv6 uses Neighbor Discovery Protocol to resolve Layer 3-to-Layer 2 information and perform related local-link functions such as router discovery and address resolution.
Review neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages., then practise related 200-301 questions on the same topic to reinforce the concept.
Neighbor Discovery Protocol (NDP) replaces ARP by resolving IPv6 addresses to MAC addresses using ICMPv6 messages.
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Last reviewed: Apr 12, 2026
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