- A
IKEv2 uses UDP port 500 for initial negotiation and can switch to UDP port 4500 for NAT traversal.
Correct because IKEv2 uses UDP 500 for standard exchanges and moves to UDP 4500 when NAT is detected, as per RFC 7296.
- B
IKEv2 requires a separate authentication phase for each security association established.
Why wrong: Incorrect because IKEv2 uses a single IKE_SA for multiple CHILD_SAs, avoiding per-SA reauthentication.
- C
IKEv2 supports EAP authentication for remote access VPNs.
Correct because IKEv2 natively supports EAP, enabling flexible authentication methods for remote users.
- D
IKEv2 uses only pre-shared keys for authentication and does not support digital certificates.
Why wrong: Incorrect because IKEv2 supports both pre-shared keys and digital certificates (RSA, ECDSA) for authentication.
- E
IKEv2 is backward compatible with IKEv1 and can interoperate with older peers.
Why wrong: Incorrect because IKEv2 is not backward compatible with IKEv1; they use different message formats and exchange procedures.
Quick Answer
The answer is that IKEv2 supports EAP authentication for remote access VPNs, which is a key characteristic distinguishing it from IKEv1. This improvement is built on IKEv2’s streamlined architecture, which uses fewer messages for Security Association (SA) establishment—reducing the exchange from nine phases in IKEv1 to just four messages in IKEv2—while also providing built-in NAT traversal and mobility support without requiring additional RFCs or workarounds. On the ENCOR 350-401 exam, this topic tests your understanding of IPsec VPN enhancements, often appearing in a "choose two" format where one correct option highlights EAP integration for remote access, and the other might reference the reduced message count or native mobility. A common trap is confusing IKEv2’s built-in features with IKEv1’s need for separate extensions; remember that IKEv2 is designed as a single, robust protocol. For a quick memory tip, think "4 for 2"—four messages for SA setup, and two key improvements: EAP and built-in NAT traversal.
CCNP VPN Technologies Practice Question
This 350-401 practice question tests your understanding of vpn technologies. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
Which two statements about IPsec IKEv2 are true? (Choose two.)
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
IKEv2 uses UDP port 500 for initial negotiation and can switch to UDP port 4500 for NAT traversal.
IKEv2 improves upon IKEv1 by using fewer messages for SA establishment and providing built-in NAT traversal and mobility support.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
IKEv2 uses UDP port 500 for initial negotiation and can switch to UDP port 4500 for NAT traversal.
- ✗
IKEv2 requires a separate authentication phase for each security association established.
Why it's wrong here
Incorrect because IKEv2 uses a single IKE_SA for multiple CHILD_SAs, avoiding per-SA reauthentication.
- ✓
IKEv2 supports EAP authentication for remote access VPNs.
Why this is correct
Correct because IKEv2 natively supports EAP, enabling flexible authentication methods for remote users.
Related concept
Static NAT maps one inside address to one outside address.
- ✗
IKEv2 uses only pre-shared keys for authentication and does not support digital certificates.
Why it's wrong here
Incorrect because IKEv2 supports both pre-shared keys and digital certificates (RSA, ECDSA) for authentication.
- ✗
IKEv2 is backward compatible with IKEv1 and can interoperate with older peers.
Why it's wrong here
Incorrect because IKEv2 is not backward compatible with IKEv1; they use different message formats and exchange procedures.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
- →
VPN Technologies — study guide chapter
Learn the concepts, then practise the questions
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VPN Technologies practice questions
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FAQ
Questions learners often ask
What does this 350-401 question test?
VPN Technologies — This question tests VPN Technologies — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: IKEv2 uses UDP port 500 for initial negotiation and can switch to UDP port 4500 for NAT traversal. — IKEv2 improves upon IKEv1 by using fewer messages for SA establishment and providing built-in NAT traversal and mobility support.
What should I do if I get this 350-401 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
About these practice questions
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Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which two statements about IPsec IKEv2 are true? (Choose two.)
medium- ✓ A.IKEv2 uses UDP port 500 for initial negotiation and can switch to UDP 4500 for NAT traversal.
- ✓ B.IKEv2 supports EAP authentication for remote access VPNs.
- C.IKEv2 uses TCP port 500 for control plane messages.
- D.IKEv2 requires a separate IPsec SA for each direction of traffic.
- E.IKEv2 is not compatible with certificate-based authentication.
Why A: IKEv2 uses UDP port 500 and 4500, supports EAP authentication, and is more robust than IKEv1. It does not use TCP, and it supports multiple simultaneous SAs.
Last reviewed: Jun 18, 2026
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