- A
The configuration creates an IPsec VTI that encrypts traffic between the two tunnel endpoints.
Correct. The tunnel mode ipsec ipv4 and crypto map create a secure tunnel, and the ACL matches the tunnel subnets.
- B
The configuration will fail because the crypto map must be applied to the tunnel interface, not the physical interface.
Why wrong: Incorrect. For IPsec VTI, the crypto map is applied to the physical interface to protect the tunnel.
- C
The configuration will only encrypt traffic from 10.0.0.0/30 to 10.0.0.4/30, but not the reverse.
Why wrong: Incorrect. The ACL is symmetric and will match traffic in both directions.
- D
The configuration uses IKEv2 because of the transform-set and crypto map.
Why wrong: Incorrect. The crypto isakmp policy indicates IKEv1; IKEv2 uses 'crypto ikev2' commands.
Quick Answer
The correct answer is that this configuration creates an IPsec VTI that encrypts traffic between the two tunnel endpoints. This is because the `tunnel mode ipsec ipv4` command under the Tunnel0 interface establishes a Virtual Tunnel Interface, which treats the tunnel as a secure, routable interface that automatically encrypts all traffic passing through it, while the crypto map applied to the physical GigabitEthernet0/0 interface protects the tunnel’s underlying transport. The access-list 100 correctly defines the interesting traffic between the two /30 subnets (10.0.0.0/30 and 10.0.0.4/30), but note that in a pure VTI deployment, the crypto map is still required on the physical interface to negotiate the IPsec SA—this is a common point of confusion on the ENCOR 350-401 exam. A frequent trap is assuming that `tunnel mode ipsec ipv4` alone handles all encryption; in reality, it creates the VTI, but the crypto map on the physical interface is what triggers IKE and IPsec. Memory tip: “VTI needs a map on the physical—the tunnel is the road, the crypto map is the toll booth.”
CCNP WAN Technologies Practice Question
This 350-401 practice question tests your understanding of wan technologies. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
interface Tunnel0 ip address 10.0.0.1 255.255.255.252
tunnel source GigabitEthernet0/0 tunnel destination 203.0.113.2 tunnel mode ipsec ipv4 !
crypto isakmp policy 10
authentication pre-share encryption aes 256 hash sha group 14 lifetime 86400 !
crypto isakmp key cisco123 address 203.0.113.2
!
crypto ipsec transform-set TSET esp-aes 256 esp-sha-hmac
mode tunnel !
crypto map CMAP 10 ipsec-isakmp
set peer 203.0.113.2 set transform-set TSET match address 100 !
interface GigabitEthernet0/0 crypto map CMAP
!
access-list 100 permit ip 10.0.0.0 0.0.0.3 10.0.0.4 0.0.0.3
What is the effect of this configuration?
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
The configuration creates an IPsec VTI that encrypts traffic between the two tunnel endpoints.
The configuration sets up a site-to-site IPsec VPN using a tunnel interface with IPsec protection. The crypto map is applied to the physical interface, and the access list defines interesting traffic between the two /30 subnets (10.0.0.0/30 and 10.0.0.4/30). This is a valid configuration for a DMVPN or static VTI, but note that the tunnel mode is 'ipsec ipv4' which is used for IPsec VTI (Virtual Tunnel Interface) and requires a crypto map on the physical interface to protect the tunnel. The access list correctly matches the tunnel networks.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The configuration creates an IPsec VTI that encrypts traffic between the two tunnel endpoints.
- ✗
The configuration will fail because the crypto map must be applied to the tunnel interface, not the physical interface.
Why it's wrong here
Incorrect. For IPsec VTI, the crypto map is applied to the physical interface to protect the tunnel.
- ✗
The configuration will only encrypt traffic from 10.0.0.0/30 to 10.0.0.4/30, but not the reverse.
Why it's wrong here
Incorrect. The ACL is symmetric and will match traffic in both directions.
- ✗
The configuration uses IKEv2 because of the transform-set and crypto map.
Why it's wrong here
Incorrect. The crypto isakmp policy indicates IKEv1; IKEv2 uses 'crypto ikev2' commands.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
Incorrect. The crypto isakmp policy indicates IKEv1; IKEv2 uses 'crypto ikev2' commands.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this 350-401 question test?
WAN Technologies — This question tests WAN Technologies — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The configuration creates an IPsec VTI that encrypts traffic between the two tunnel endpoints. — The configuration sets up a site-to-site IPsec VPN using a tunnel interface with IPsec protection. The crypto map is applied to the physical interface, and the access list defines interesting traffic between the two /30 subnets (10.0.0.0/30 and 10.0.0.4/30). This is a valid configuration for a DMVPN or static VTI, but note that the tunnel mode is 'ipsec ipv4' which is used for IPsec VTI (Virtual Tunnel Interface) and requires a crypto map on the physical interface to protect the tunnel. The access list correctly matches the tunnel networks.
What should I do if I get this 350-401 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 350-401 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Last reviewed: Jun 18, 2026
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.
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