- A
The number of concurrent tunnels allowed.
Correct. The firewall may limit concurrent SAs per gateway.
- B
The IPSec crypto profile.
Why wrong: Incorrect. Crypto profile defines algorithms, not capacity.
- C
The IKE gateway mode.
Why wrong: Incorrect. Mode affects IKE version, not number of SAs.
- D
The tunnel monitor settings.
Why wrong: Incorrect. Monitor settings affect passive monitoring, not SA establishment.
Question 99 of 516
IPSec Proxy ID Tunnel Limit: Only One SA Established? Check Concurrent Tunnel Count
This PCNSE practice question tests your understanding of secure access and vpn. 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.
A network engineer configures an IPSec tunnel with multiple proxy IDs for different subnets. After committing, only one proxy ID establishes IPsec SAs. What should the engineer check?
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 number of concurrent tunnels allowed.
Option A is correct because Palo Alto Networks firewalls have a default limit on the number of concurrent IPsec tunnels. When multiple proxy IDs are configured, each proxy ID requires its own IPsec security association (SA). If the tunnel limit is reached, only the first proxy ID establishes SAs, and subsequent ones fail. Checking and increasing the 'Number of Tunnels' setting under the tunnel interface or global IPSec configuration resolves this.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 number of concurrent tunnels allowed.
- ✗
The IPSec crypto profile.
Why it's wrong here
Incorrect. Crypto profile defines algorithms, not capacity.
- ✗
The IKE gateway mode.
Why it's wrong here
Incorrect. Mode affects IKE version, not number of SAs.
- ✗
The tunnel monitor settings.
Why it's wrong here
Incorrect. Monitor settings affect passive monitoring, not SA establishment.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the issue is with crypto profile mismatches or IKE gateway settings, but Palo Alto specifically tests the knowledge that each proxy ID consumes a separate tunnel slot, and the tunnel count limit is a common misconfiguration that causes only one proxy ID to work.
Detailed technical explanation
How to think about this question
Under the hood, each proxy ID in an IPSec tunnel on a Palo Alto firewall creates a separate Phase 2 SA pair (inbound/outbound). The firewall enforces a configurable maximum number of tunnels (default is 1 for some models or configurations) to prevent resource exhaustion. This limit is set per tunnel interface or globally under Network > IPSec Tunnels > Tunnel Settings. In real-world scenarios, if an engineer configures proxy IDs for 10 subnets but the tunnel limit is 5, only the first 5 subnets will have working IPSec SAs, causing partial connectivity.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Secure Access and VPN — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Secure Access and VPN — This question tests Secure Access and VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The number of concurrent tunnels allowed. — Option A is correct because Palo Alto Networks firewalls have a default limit on the number of concurrent IPsec tunnels. When multiple proxy IDs are configured, each proxy ID requires its own IPsec security association (SA). If the tunnel limit is reached, only the first proxy ID establishes SAs, and subsequent ones fail. Checking and increasing the 'Number of Tunnels' setting under the tunnel interface or global IPSec configuration resolves this.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This PCNSE practice question is part of Courseiva's free Palo Alto 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 PCNSE exam.
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