300-410 VPN Technologies Practice Question
A network engineer is configuring a site-to-site IPsec VPN between two Cisco IOS routers. The engineer wants to ensure that only traffic from the 10.1.1.0/24 subnet to the 10.2.2.0/24 subnet is encrypted, while all other traffic is sent unencrypted. Which type of ACL should be used in the crypto map to match this traffic?
⚠ Common exam trap
Candidates often confuse the direction of the ACL: the crypto ACL permits interesting traffic, not denies it.
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
✓
An extended ACL that permits IP traffic from 10.1.1.0/24 to 10.2.2.0/24 and denies all other traffic.
The crypto ACL must permit the specific traffic that should be encrypted and implicitly deny all other traffic. An extended ACL that permits IP traffic from 10.1.1.0/24 to 10.2.2.0/24 and denies all other traffic achieves this. Standard ACLs cannot match destination addresses, and denying the desired traffic or permitting all traffic would be incorrect.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
A standard ACL that permits the 10.1.1.0/24 subnet.
Why it's wrong here
A standard ACL can only match source addresses, not destination addresses. The crypto ACL must match both source and destination to identify the traffic flow between the two subnets. Therefore, a standard ACL would not correctly define the interesting traffic for this site-to-site VPN.
- ✓
An extended ACL that permits IP traffic from 10.1.1.0/24 to 10.2.2.0/24 and denies all other traffic.
Why this is correct
This is correct because the crypto ACL defines interesting traffic that should be encrypted. It must permit the specific source/destination subnet pair and implicitly deny everything else. The implicit deny ensures other traffic is not encrypted, and the ACL is used to match traffic for the VPN.
- ✗
A named ACL that permits all IP traffic.
Why it's wrong here
Permitting all IP traffic would cause all traffic to be encrypted, not just the traffic between the specified subnets. The requirement is to encrypt only traffic between 10.1.1.0/24 and 10.2.2.0/24. Therefore, a permit-all ACL is too broad and does not meet the requirement.
- ✗
An extended ACL that denies IP traffic from 10.1.1.0/24 to 10.2.2.0/24 and permits all other traffic.
Why it's wrong here
This ACL would deny the traffic that should be encrypted and permit everything else. The crypto ACL is used to match traffic that should be encrypted, so it must permit the desired traffic, not deny it. Denying the traffic would prevent it from being encrypted.
Visual reference
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
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.