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300-410 Practice Question: The default hash algorithm for IKEv1 phase 1 in…
What is the default hash algorithm for IKEv1 phase 1 in Cisco IOS when not explicitly configured?
⚠ Common exam trap
Cisco often tests the misconception that IKEv1 has no default hash or that SHA-1 is the default, when in fact MD5 is the default for IKEv1 phase 1 in Cisco IOS.
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
✓
MD5
In Cisco IOS, when IKEv1 phase 1 parameters are not explicitly configured, the default hash algorithm is MD5. This is because the default IKE proposal in Cisco IOS includes MD5 as the hash algorithm, along with DES encryption and Diffie-Hellman group 1. MD5 was chosen historically for its lower computational overhead, though it is now considered cryptographically weak.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SHA-1
Why it's wrong here
SHA-1 is not the default; MD5 is.
- ✓
MD5
Why this is correct
MD5 is the default hash algorithm for IKEv1.
- ✗
SHA-256
Why it's wrong here
SHA-256 requires explicit configuration.
- ✗
No default; hash must be configured
Why it's wrong here
MD5 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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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.