The answer is to configure a route-based VPN and use dynamic routing protocols to advertise routes. This is the most efficient way to add a spoke in a hub-and-spoke IPsec VPN because a route-based VPN decouples the tunnel interface from the phase2 selectors, allowing the hub to use a single phase2 selector (or a wildcard) for all spokes instead of adding a new one for each spoke. Dynamic routing protocols like BGP or OSPF then automatically exchange routes between the hub and new spoke, eliminating manual configuration of static routes or additional phase2 selectors. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this question tests your understanding of scalability in IPsec VPN design—the common trap is thinking you must add another phase2 selector for each new spoke, which works but is inefficient. Remember the memory tip: “One tunnel, many routes—dynamic routing saves the day.”
NSE4 Authentication and VPN Practice Question
This NSE4 practice question tests your understanding of authentication 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.
You have a hub-and-spoke IPsec VPN with 10 spokes. The central FortiGate (hub) has 10 phase2 selectors, one for each spoke. You need to add a new spoke. What is the MOST efficient way to configure the hub?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure a route-based VPN and use dynamic routing protocols to advertise routes
Using a route-based VPN with dynamic routing (e.g., BGP or OSPF) eliminates the need for multiple phase2 selectors. The hub only needs one phase2 selector for each spoke or can use a wildcard. Route-based VPN is more scalable.
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.
✓
Configure a route-based VPN and use dynamic routing protocols to advertise routes
Why this is correct
Route-based VPN with dynamic routing scales automatically as new spokes are added.
This works but is not the most efficient; manual changes required for each new spoke.
✗
Replace all phase2 selectors with a single policy-based VPN
Why it's wrong here
Policy-based VPN still requires individual policies per spoke; not efficient.
✗
Use a single phase2 selector with 0.0.0.0/0.0.0.0 for all spokes
Why it's wrong here
This may cause conflicts and is not recommended; security policy should be specific.
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 NSE4 OSPF questions on adjacency and route selection.
Authentication and VPN — This question tests Authentication and VPN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: Configure a route-based VPN and use dynamic routing protocols to advertise routes — Using a route-based VPN with dynamic routing (e.g., BGP or OSPF) eliminates the need for multiple phase2 selectors. The hub only needs one phase2 selector for each spoke or can use a wildcard. Route-based VPN is more scalable.
What should I do if I get this NSE4 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 NSE4 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Question Discussion
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