- A
The firewall's asymmetric routing detection is dropping traffic; disable asymmetric routing enforcement.
Why wrong: Asymmetric routing detection affects return traffic, not outbound path selection.
- B
The HA configuration has ECMP disabled; enable ECMP in the dataplane settings on the active firewall.
ECMP allows the firewall to use multiple equal-cost routes for load balancing; it must be enabled.
- C
The BGP configuration on the passive firewall is not identical to the active one; apply the same BGP configuration to both.
Why wrong: The passive firewall's BGP config does not impact the active firewall's routing table.
- D
The passive firewall is not advertising routes to the ISPs because HA state synchronization is not enabled; enable state synchronization.
Why wrong: State sync does not affect route advertisement; BGP peers on the passive firewall are independent.
ECMP in HA Active/Passive — Why Load Balancing Fails After Failover
This PCNSE practice question tests your understanding of deploy and configure firewalls. 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 company has deployed a Palo Alto Networks firewall in an active/passive high-availability (HA) pair. The firewall uses BGP for dynamic routing with two upstream ISPs to provide load-balanced internet connectivity. After an HA failover event, the network team notices that outbound traffic from internal hosts is now using only one of the two ISPs, even though BGP sessions are established on both firewalls and the passive firewall has learned the same routes as the active one. The security policy permits all outbound traffic. No changes were made to the BGP configuration. Which of the following is the most likely cause of this behavior, and what is the appropriate solution?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 HA configuration has ECMP disabled; enable ECMP in the dataplane settings on the active firewall.
B is correct because in an active/passive HA pair, ECMP (Equal-Cost Multi-Path) is disabled by default on the dataplane. Even though BGP sessions are established and routes are learned, the active firewall will only install a single best path per prefix unless ECMP is explicitly enabled in the dataplane settings. This causes outbound traffic to use only one ISP after failover, as the firewall is not load-balancing across the two equal-cost BGP routes.
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 firewall's asymmetric routing detection is dropping traffic; disable asymmetric routing enforcement.
Why it's wrong here
Asymmetric routing detection affects return traffic, not outbound path selection.
- ✓
The HA configuration has ECMP disabled; enable ECMP in the dataplane settings on the active firewall.
Why this is correct
ECMP allows the firewall to use multiple equal-cost routes for load balancing; it must be enabled.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The BGP configuration on the passive firewall is not identical to the active one; apply the same BGP configuration to both.
- ✗
The passive firewall is not advertising routes to the ISPs because HA state synchronization is not enabled; enable state synchronization.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume BGP sessions being established and routes being learned automatically results in load balancing, but PAN-OS requires explicit ECMP enablement in the dataplane to use multiple equal-cost paths for forwarding.
Detailed technical explanation
How to think about this question
ECMP in PAN-OS is a dataplane-level setting that must be explicitly enabled under Device > Setup > Session > Session Settings. When ECMP is disabled, the firewall selects only the best route per prefix based on the routing table's tie-breaking rules (e.g., lowest route metric, then lowest next-hop IP). In a real-world scenario, if both ISPs advertise the same prefix with equal metrics, the firewall will pin traffic to one ISP until that route is withdrawn, causing suboptimal bandwidth utilization and potential congestion.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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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FAQ
Questions learners often ask
What does this PCNSE question test?
Deploy and Configure Firewalls — This question tests Deploy and Configure Firewalls — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The HA configuration has ECMP disabled; enable ECMP in the dataplane settings on the active firewall. — B is correct because in an active/passive HA pair, ECMP (Equal-Cost Multi-Path) is disabled by default on the dataplane. Even though BGP sessions are established and routes are learned, the active firewall will only install a single best path per prefix unless ECMP is explicitly enabled in the dataplane settings. This causes outbound traffic to use only one ISP after failover, as the firewall is not load-balancing across the two equal-cost BGP routes.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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