hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Which authentication method is used by default in…
Which authentication method is used by default in IKEv1 main mode for IPsec site-to-site VPN on Cisco IOS?
⚠ Common exam trap
Cisco often tests the misconception that IKEv1 has no default authentication method, leading candidates to choose 'No default; authentication must be explicitly configured' when in fact pre-shared keys are the default.
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 keys
In Cisco IOS, IKEv1 main mode for IPsec site-to-site VPN defaults to pre-shared keys (PSK) as the authentication method. This is because PSK is the simplest to configure and does not require a public key infrastructure (PKI), making it the default choice when no other authentication method is explicitly specified. The configuration commands like 'crypto isakmp key' directly implement PSK authentication.
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 signatures
Why it's wrong here
RSA signatures require digital certificates and are not the default.
- ✓
Pre-shared keys
Why this is correct
PSK is the default authentication method for IKEv1.
- ✗
Elliptic Curve Digital Signature Algorithm (ECDSA)
Why it's wrong here
ECDSA is not a default; it is used in advanced configurations.
- ✗
No default; authentication must be explicitly configured
Why it's wrong here
PSK is the default if no method is specified.
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
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.