mediumMultiple ChoiceObjective-mapped
300-410 Practice Question: Which statement correctly describes the behavior…
Which statement correctly describes the behavior of IPv6 Unicast Reverse Path Forwarding (uRPF) in strict mode?
⚠ Common exam trap
Cisco often tests the distinction between strict and loose mode, and the trap here is that candidates confuse 'route points back to that interface' with 'route is a connected route,' leading them to incorrectly select Option B.
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
✓
It verifies that the source address is reachable via the same interface and that the route points back to that interface.
IPv6 uRPF strict mode requires that the source address of an incoming packet is reachable via the exact same interface on which the packet arrived, and that the best matching route in the FIB points back to that interface. This prevents spoofed traffic by ensuring the source is topologically correct from the router's perspective, as defined in RFC 3704.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It verifies that the source address is in the routing table, but does not check the incoming interface.
Why it's wrong here
That describes loose mode, not strict mode.
- ✗
It checks that the source address is reachable via the same interface and that the route is a connected route.
Why it's wrong here
The route does not have to be connected; it must point back to the same interface.
- ✓
It verifies that the source address is reachable via the same interface and that the route points back to that interface.
Why this is correct
This is the definition of strict mode uRPF.
- ✗
It only checks that the source address is not a multicast or link-local address.
Why it's wrong here
uRPF does not filter based on address type; it checks reachability.
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Senior Network & Security Engineer · founder of Courseiva
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