Quick Answer
The answer is that floating static routes were not configured on the passive firewall. This is correct because in an active/passive HA pair, static routes are not automatically synchronized from the active to the passive firewall; the passive unit must have its own static routes pre-configured, typically as floating static routes with a higher administrative distance to prevent conflicts during normal operation. When a failover occurs, the new active firewall—formerly passive—lacks the default route, causing traffic to fail. On the PCNSE exam, this scenario tests your understanding of HA route synchronization limitations and the distinction between dynamic and static route propagation. A common trap is assuming that all configurations, including static routes, are mirrored automatically. Remember the memory tip: “Passive needs its own path—floating routes prevent the crash.”
This PCNSE practice question tests your understanding of managing troubleshooting and high availability. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
An engineer notices that after an HA failover, the new active firewall is not passing traffic. The show running ip route command shows the default route is missing. What is the most likely cause?
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.
Floating static routes were not configured on the passive firewall.
Floating static routes are not synchronized and must be configured on both firewalls.
Static routes were not synchronized.
Why wrong: Static routes are synchronized via HA.
OSPF routes were not synchronized.
Why wrong: OSPF routes are synchronized via HA.
BGP routes were not synchronized.
Why wrong: BGP routes are synchronized via HA.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Floating static routes were not configured on the passive firewall.
In an active/passive HA pair, static routes are not automatically synchronized from the active to the passive firewall. The passive firewall must have its own static routes configured, often as floating static routes with a higher administrative distance to avoid conflicts during normal operation. When a failover occurs, the new active firewall (formerly passive) lacks the default route because it was never configured or synchronized, causing traffic to fail.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Floating static routes were not configured on the passive firewall.
Why this is correct
Floating static routes are not synchronized and must be configured on both firewalls.
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.
Static routes were not synchronized.
Why it's wrong here
Static routes are synchronized via HA.
OSPF routes were not synchronized.
Why it's wrong here
OSPF routes are synchronized via HA.
BGP routes were not synchronized.
Why it's wrong here
BGP routes are synchronized via HA.
Common exam traps
The trap here is that candidates assume all routes are synchronized in HA, but PAN-OS only synchronizes dynamic routing protocol states and not static route configuration, requiring explicit configuration on both peers.
Detailed technical explanation
In PAN-OS HA, only session state, configuration (including route tables), and some runtime data are synchronized from active to passive, but static routes must be explicitly configured on both firewalls. Floating static routes use a higher administrative distance (e.g., 200 vs. default 10) so they are only active when the primary route is lost, ensuring seamless failover. Without them, the new active firewall has no default route until manually added or learned via dynamic routing.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
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
Managing Troubleshooting and High Availability — This question tests Managing Troubleshooting and High Availability — Read the scenario before looking for a memorised answer..
The correct answer is: Floating static routes were not configured on the passive firewall. — In an active/passive HA pair, static routes are not automatically synchronized from the active to the passive firewall. The passive firewall must have its own static routes configured, often as floating static routes with a higher administrative distance to avoid conflicts during normal operation. When a failover occurs, the new active firewall (formerly passive) lacks the default route because it was never configured or synchronized, causing traffic to fail.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
About these practice questions
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Same concept, more angles
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. A company has two Palo Alto Networks firewalls configured in an active/passive HA pair. During a failover test, the passive firewall becomes active, but traffic stops passing through the new active firewall. The management interface on the new active firewall is reachable. What is the most likely cause?
hardWhy D: Option D is correct because when a passive firewall becomes active, it must process all new session setups from scratch. If the session setup rate exceeds the new active firewall's capacity (e.g., due to licensing limits on session count or throughput), traffic will be dropped even though the management interface remains reachable. The management plane is separate from the data plane, so management access can still work while forwarding fails.
Variation 2. A company has two Palo Alto Networks firewalls configured in active/passive HA. During a failover test, the passive firewall becomes active but traffic is not passing. The active firewall shows the correct configuration and licenses. Which action is most likely to resolve the issue?
mediumWhy C: Option C is correct because the most likely cause of traffic failure after a failover is that the configuration on the newly active firewall is out of sync with the original active firewall. In active/passive HA, configuration synchronization (config sync) is typically enabled, but if it was not performed before the failover or if the passive device had a stale configuration, critical settings such as interface IPs, security policies, or routing entries may be missing or incorrect. Performing a configuration synchronization from the original active firewall ensures the new active device has the exact same configuration, restoring traffic flow.
Last reviewed: Jun 11, 2026
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