easyMultiple Choice
350-401 Practice Question: Which IPsec protocol provides both encryption and…
Which IPsec protocol provides both encryption and authentication within a single ESP header?
⚠ Common exam trap
Cisco often tests the misconception that AH provides encryption or that ESP cannot provide authentication, when in fact ESP includes an optional authentication field (ICV) and is the standard for combined encryption and authentication in IPsec.
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
✓
ESP (Encapsulating Security Payload)
ESP (Encapsulating Security Payload) provides both encryption for data confidentiality and authentication (via an optional Integrity Check Value) within a single ESP header. Unlike AH, ESP can encrypt the payload while also offering integrity and origin authentication, making it the correct choice for combined services in a single header.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AH (Authentication Header)
Why it's wrong here
AH (Authentication Header) provides integrity and data-origin authentication for IP packets by computing a keyed hash over the entire packet, but it does not encrypt any portion of the payload. Because the IP header fields that AH protects are often modified by NAT, AH can break in NAT environments. Since it offers no confidentiality, AH cannot be used to meet a data encryption requirement.
- ✓
ESP (Encapsulating Security Payload)
Why this is correct
ESP (Encapsulating Security Payload) is the correct choice because it is designed to provide confidentiality via encryption, and it can also offer optional integrity and authentication for the protected payload. In tunnel mode, ESP encapsulates the entire original IP packet and encrypts its contents, making it unreadable to eavesdroppers. This makes ESP the standard IPsec protocol for secure VPN data transmission, as it directly satisfies the need for encryption.
- ✗
IKE (Internet Key Exchange)
Why it's wrong here
IKE (Internet Key Exchange) is a control-plane protocol that negotiates security associations (SAs) and performs authenticated key exchange using mechanisms like Diffie-Hellman, but it does not transport or encrypt user data. IKE operates on UDP ports 500 and 4500 to set up the parameters that ESP (or AH) will later use for actual packet processing. Therefore, IKE is a supporting protocol, not an IPsec data-plane encryption protocol, so it cannot be the answer.
- ✗
GRE (Generic Routing Encapsulation)
Why it's wrong here
GRE (Generic Routing Encapsulation) is a tunneling protocol that encapsulates arbitrary network-layer protocols inside IP packets, but it does not include any security features—no encryption, no authentication, and no confidentiality. GRE traffic is sent in plaintext, meaning an attacker can read the entire inner payload if they capture the packets. While GRE is often combined with IPsec to secure the tunnel, GRE itself provides no encryption, so it fails the requirement.
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 350-401 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 350-401 exam.