JNCIS-ENT Tunnels Practice Question
You are configuring a GRE tunnel over an IPv4 network, but you want to secure the GRE traffic using IPsec (GRE over IPsec). In Junos, how is this typically structured on SRX or MX devices?
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
✓
Traffic is encapsulated in GRE, and the resulting GRE packets are subsequently protected by IPsec VPN policies.
GRE over IPsec involves encapsulating traffic in GRE first, and then applying IPsec protection to the GRE packets by referencing the tunnel or transport zones/policies.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
GRE and IPsec operate simultaneously as a single unified protocol without nested headers.
Why it's wrong here
They are distinct protocols; GRE over IPsec requires nested encapsulation.
- ✗
IPsec encapsulates the traffic first, and GRE wraps the encrypted payload.
Why it's wrong here
Wrapping encrypted packets in GRE defeats the security and is not the standard GRE over IPsec architecture.
- ✗
IPsec replaces the GRE header entirely while maintaining GRE interface numbers.
Why it's wrong here
IPsec does not replace GRE headers; IPsec adds ESP/AH headers.
- ✓
Traffic is encapsulated in GRE, and the resulting GRE packets are subsequently protected by IPsec VPN policies.
Why this is correct
GRE over IPsec tunnels route traffic through the GRE interface first, and IPsec crypto maps or security policies encrypt the outer GRE packets.
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.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Juniper Networks exam blueprint
This JNCIS-ENT practice question is part of Courseiva's free Juniper Networks 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 JNCIS-ENT exam.