350-401 Security Practice Question
A network engineer is implementing IPsec VPN on a Cisco IOS XE router to connect a branch office to headquarters. The engineer must ensure that the IKEv2 negotiation uses strong authentication and that the data plane is protected with integrity and encryption. Which two configuration elements are required to achieve this? (Choose two.)
⚠ Common exam trap
Watch out — candidates often confuse IKEv1 and IKEv2 configuration syntax, and assuming a crypto ACL or lifetime setting alone can provide authentication and encryption.
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
✓
Configure an IKEv2 keyring or PKI trustpoint to authenticate the peers.
IKEv2 requires peer authentication, provided by a keyring with pre-shared keys or a PKI trustpoint. The data plane is protected by an IPsec transform set that specifies ESP encryption and authentication algorithms. Both elements must be configured and referenced correctly in the IPsec profile or crypto map. The other options either apply to IKEv1 or do not provide the required security functions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure an IKEv2 keyring or PKI trustpoint to authenticate the peers.
Why this is correct
IKEv2 requires peer authentication before establishing the IPsec SA. A keyring with pre-shared keys or a PKI trustpoint with certificates provides that authentication. Without it, IKEv2 negotiation fails. This element is mandatory for strong authentication and directly supports the requirement. It is separate from the IPsec transform set, which protects the data plane, so both are needed in the overall configuration.
- ✗
Configure 'crypto isakmp policy' with pre-shared key authentication for IKEv1.
Why it's wrong here
The 'crypto isakmp policy' command configures IKEv1, not IKEv2. The scenario specifies IKEv2 negotiation. IKEv1 policies use different syntax and are not used when IKEv2 is configured. This option would not apply to the IKEv2 negotiation and therefore does not meet the stated requirement for strong authentication in an IKEv2 deployment.
- ✓
Configure an IPsec transform set specifying ESP encryption and authentication algorithms.
Why this is correct
The transform set defines how the data plane is protected, including ESP encryption (e.g., AES) and authentication (e.g., SHA). It is referenced by the IPsec profile or crypto map. Without a transform set, the data plane has no encryption or integrity protection. This directly fulfills the requirement for data plane protection and is a required element alongside IKEv2 authentication.
- ✗
Configure 'crypto ipsec profile' with 'set security-association lifetime seconds 3600' only.
Why it's wrong here
The lifetime setting controls how long the IPsec SA remains valid before rekeying. It does not define encryption or authentication algorithms, nor does it authenticate peers. A profile with only a lifetime setting lacks the transform set reference and would not provide data plane protection. This option is incomplete and does not satisfy the requirement for integrity and encryption.
- ✗
Configure a crypto ACL with 'permit ip any any' to match all traffic.
Why it's wrong here
A crypto ACL defines interesting traffic that should be encrypted. While often needed, it does not provide authentication or data plane protection by itself. Using 'permit ip any any' would encrypt all traffic, which may be undesirable and does not satisfy the specific requirement for strong authentication and integrity/encryption algorithms. It is not a required element for those goals.
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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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