PCNSE Practice Question: Managing Troubleshooting and High Availability
This PCNSE practice question tests your understanding of managing troubleshooting and high availability. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 medium-sized enterprise has two Palo Alto Networks PA-5250 firewalls configured in an active/passive HA pair with session synchronization and configuration synchronization enabled. The HA1 link is a direct copper cable, and the HA2 link is also a direct copper cable. The firewalls are connected to two upstream routers (R1 and R2) and two downstream switches (S1 and S2). The network uses OSPF for dynamic routing. The active firewall (FW-A) is connected to R1 and S1, while the passive firewall (FW-P) is connected to R2 and S2. The OSPF cost is set symmetrically on both sides. During a maintenance window, the network team shuts down the HA1 and HA2 links on both firewalls to test failover behavior. After the links are brought back up, the firewalls are in a state of 'non-functional' and 'suspended'. The team suspects the HA configuration is broken. What is the most likely cause and the best course of action to restore HA?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reboot both firewalls after verifying the HA configuration and that the links are operationally up
Option D is correct. When HA1 and HA2 links are shut down simultaneously, both firewalls may enter suspended state due to loss of all HA keepalives. The recommended recovery is to reboot both firewalls after verifying configuration. Option A is wrong because changing preemptive mode does not address the suspension. Option B is wrong because creating a dedicated HA management network does not fix the current issue. Option C is wrong because different software versions are not allowed in HA.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Upgrade both firewalls to the same software version and then re-initialize HA
Why it's wrong here
Software version is assumed same; re-initializing may help but the root cause is not software version.
✗
Change the HA mode to active/active and enable asymmetric routing
Why it's wrong here
Does not resolve the suspended state.
✓
Reboot both firewalls after verifying the HA configuration and that the links are operationally up
Why this is correct
Rebooting recovers from suspended state; links are up now.
Clue confirmation
The clue words "best", "most likely" in the question point toward this answer.
Configure a dedicated management interface for HA1 communication and ensure HA2 is on a different subnet
Why it's wrong here
HA1 and HA2 must be on the same subnet; this suggestion is incorrect and does not fix suspension.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related PCNSE OSPF questions on adjacency and route selection.
Managing Troubleshooting and High Availability — This question tests Managing Troubleshooting and High Availability — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Reboot both firewalls after verifying the HA configuration and that the links are operationally up — Option D is correct. When HA1 and HA2 links are shut down simultaneously, both firewalls may enter suspended state due to loss of all HA keepalives. The recommended recovery is to reboot both firewalls after verifying configuration. Option A is wrong because changing preemptive mode does not address the suspension. Option B is wrong because creating a dedicated HA management network does not fix the current issue. Option C is wrong because different software versions are not allowed in HA.
What should I do if I get this PCNSE question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related PCNSE OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "best", "most likely". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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