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350-401 Practice Question: Which three statements about NAT traversal and…
Which three statements about NAT traversal and translation are true? (Choose three.)
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
✓
IPsec NAT traversal uses UDP encapsulation on port 4500 to allow ESP traffic to pass through a NAT device.
NAT traversal for IPsec uses UDP encapsulation (4500) to allow ESP through NAT devices. NAT can translate both source and destination addresses simultaneously in different scenarios. The ip nat outside source command translates source addresses of packets entering the outside interface. NAT can cause issues with applications that embed IP addresses in payload (e.g., FTP, SIP). NAT does not translate MAC addresses, only IP and port information. The ip nat inside destination command translates destination addresses of packets entering the inside interface.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
IPsec NAT traversal uses UDP encapsulation on port 4500 to allow ESP traffic to pass through a NAT device.
Why this is correct
Correct because NAT-T encapsulates ESP in UDP port 4500 to avoid issues with NAT modifying the IP header.
- ✓
The ip nat outside source command translates the source IP address of packets arriving on the outside interface.
Why this is correct
Correct because this command performs source NAT on traffic entering the outside interface, typically for overlapping networks.
- ✓
NAT can translate both source and destination IP addresses in the same packet for different translation rules.
Why this is correct
Correct because a packet can undergo both source NAT (on inside) and destination NAT (on outside) depending on configuration.
- ✗
NAT automatically translates IP addresses embedded in application-layer payloads such as FTP or SIP.
Why it's wrong here
Incorrect because NAT does not inspect or modify application payloads unless an ALG is configured; it only changes IP/port headers.
- ✗
The ip nat inside destination command translates the destination MAC address of packets entering the inside interface.
Why it's wrong here
Incorrect because ip nat inside destination translates destination IP addresses, not MAC addresses; NAT operates at Layer 3.
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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Last reviewed: Jun 18, 2026
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