- A
IPsec
Why wrong: IPsec can secure IPv6 traffic but is not specifically used for ND message authentication in FHS.
- B
SEND
Correct. SEND (Secure Neighbor Discovery) uses CGAs and RSA signatures to authenticate ND messages.
- C
SSL/TLS
Why wrong: SSL/TLS is used for transport layer security, not for ND message authentication.
- D
MACsec
Why wrong: MACsec provides link-layer encryption but is not specific to ND message authentication.
Question 1,976 of 2,152
300-410 IPv6 First Hop Security Practice Question
This 300-410 practice question tests your understanding of ipv6 first hop security. 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.
In IPv6 FHS, which protocol is used to secure Neighbor Discovery messages with cryptographic authentication?
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
✓
SEND
B is correct because SEND (Secure Neighbor Discovery, RFC 3971) uses Cryptographically Generated Addresses (CGAs) and RSA signatures to authenticate Neighbor Discovery (ND) messages, protecting against threats like Neighbor Advertisement spoofing and Duplicate Address Detection (DAD) attacks. Unlike IPsec, SEND does not require a pre-established security infrastructure or key management, making it practical for securing ND in IPv6 first-hop segments.
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.
- ✗
IPsec
Why it's wrong here
IPsec can secure IPv6 traffic but is not specifically used for ND message authentication in FHS.
- ✓
SEND
Why this is correct
Correct. SEND (Secure Neighbor Discovery) uses CGAs and RSA signatures to authenticate ND messages.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
SSL/TLS
Why it's wrong here
SSL/TLS is used for transport layer security, not for ND message authentication.
- ✗
MACsec
Why it's wrong here
MACsec provides link-layer encryption but is not specific to ND message authentication.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that IPsec is the universal security solution for IPv6, but the trap here is that SEND is the specific protocol designed to authenticate Neighbor Discovery messages, while IPsec is used for general IPv6 traffic protection and requires a different trust model.
Detailed technical explanation
How to think about this question
SEND uses CGAs, which bind a public key to an IPv6 address by hashing the public key and other parameters into the interface identifier, ensuring the address owner possesses the corresponding private key. When a router or host sends an ND message (e.g., Router Advertisement or Neighbor Solicitation), it includes a CGA option and a digital signature; the receiver verifies the signature using the public key embedded in the CGA, preventing address spoofing without a central authority. In real-world deployments, SEND is critical in enterprise networks where rogue RA attacks could redirect traffic, but it requires careful CGA parameter management and can add CPU overhead due to signature verification.
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 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.
Quick reference
VPN Protocol Comparison
| Protocol | Port | Encryption | Authentication | Use Case |
|---|---|---|---|---|
| IKEv2 / IPsec | UDP 500 / 4500 | AES-256 | Certificates / PSK | Site-to-site & remote access |
| SSL / TLS VPN | TCP 443 | TLS 1.3 | Certificates / MFA | Clientless remote access |
| L2TP / IPsec | UDP 1701 | AES (IPsec) | PSK / Certificates | Legacy remote access |
| WireGuard | UDP 51820 | ChaCha20 | Public keys | Modern high-performance VPN |
| PPTP | TCP 1723 | MPPE (weak) | MS-CHAPv2 | Legacy — avoid in production |
PPTP is considered insecure. IKEv2/IPsec and SSL VPN are the current recommended options.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 300-410 question test?
IPv6 First Hop Security — This question tests IPv6 First Hop Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SEND — B is correct because SEND (Secure Neighbor Discovery, RFC 3971) uses Cryptographically Generated Addresses (CGAs) and RSA signatures to authenticate Neighbor Discovery (ND) messages, protecting against threats like Neighbor Advertisement spoofing and Duplicate Address Detection (DAD) attacks. Unlike IPsec, SEND does not require a pre-established security infrastructure or key management, making it practical for securing ND in IPv6 first-hop segments.
What should I do if I get this 300-410 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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Last reviewed: Jul 4, 2026
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