hardMultiple ChoiceObjective-mapped
300-410 Practice Question: In Cisco IOS, what is the default IKEv1 phase 1…
In Cisco IOS, what is the default IKEv1 phase 1 authentication method when using a pre-shared key and no explicit authentication is configured?
⚠ Common exam trap
Cisco often tests the misconception that authentication must always be explicitly configured, leading candidates to choose 'No default' when in fact the default is pre-shared key for pre-shared key configurations.
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
✓
Pre-shared key
When no explicit authentication method is configured for IKEv1 phase 1 and a pre-shared key is used, Cisco IOS defaults to 'pre-shared key' authentication. This is because the pre-shared key itself defines the authentication mechanism; the router automatically selects the appropriate authentication method based on the configured key material.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RSA encrypted nonces
Why it's wrong here
RSA encrypted nonces require certificate configuration and are not default.
- ✓
Pre-shared key
Why this is correct
IOS defaults to pre-shared key authentication when not specified.
- ✗
Digital signatures (RSA-SIG)
Why it's wrong here
Digital signatures are not the default.
- ✗
No default; authentication must be explicitly set
Why it's wrong here
Pre-shared key is the default.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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