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300-410 Practice Question: In IPv6 FHS, which protocol is used to secure…
In IPv6 FHS, which protocol is used to secure Neighbor Discovery messages with cryptographic authentication?
⚠ Common exam trap
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.
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.
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.
- ✗
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.
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.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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