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300-410 Practice Question: Which THREE symptoms indicate that IPv6 unicast…
Which THREE symptoms indicate that IPv6 unicast RPF is misconfigured or failing on an interface? (Choose THREE.)
⚠ Common exam trap
Cisco often tests the distinction between strict and loose mode RPF, and the trap here is that candidates may incorrectly assume that the presence of the 'ipv6 verify unicast source reachable-via any' command itself is a symptom of misconfiguration, when in fact it is a legitimate configuration for loose mode.
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
✓
Traffic from a valid source IP is being dropped on the interface.
IPv6 unicast RPF (uRPF) drops traffic when the source address is not reachable via the incoming interface according to the FIB. If a valid source IP is being dropped, it indicates that the RPF check is failing, often due to asymmetric routing or a missing route in the FIB for that source prefix.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Traffic from a valid source IP is being dropped on the interface.
Why this is correct
uRPF drops packets when the source IP is not reachable via the incoming interface, even if the IP is valid.
- ✓
The router logs 'IPv6 unicast RPF drop' messages.
Why this is correct
Syslog messages can indicate uRPF drops when logging is enabled.
- ✗
The command 'ipv6 verify unicast source reachable-via any' is present in the running config.
Why it's wrong here
The presence of `ipv6 verify unicast source reachable-via any` indicates that IPv6 unicast RPF is *enabled* on the interface, specifically in its most permissive mode. This command does not signify misconfiguration or failure; rather, it confirms RPF is active. It is tempting because it is an RPF command, but `reachable-via any` simply checks if the source IP exists in the FIB, allowing traffic from any interface if a route exists. This mode is correctly utilised to prevent IP spoofing where multiple legitimate ingress paths are possible.
- ✗
High CPU utilization is observed due to RPF processing.
Why it's wrong here
uRPF is typically performed in hardware (CEF) and does not cause high CPU.
- ✓
The 'show ipv6 interface' output shows an increasing 'RPF drops' counter.
Why this is correct
The 'show ipv6 interface' command displays a counter for uRPF drops, indicating drops are occurring.
Quick reference
Asymmetric Encryption Algorithm Comparison
| Algorithm | Key Exchange | Signatures | Equivalent Security Key | Notes |
|---|---|---|---|---|
| RSA-3072 | Yes | Yes | 128-bit | Widely deployed; slow for bulk data |
| ECDSA P-256 | No | Yes | 128-bit | Fast signatures; standard TLS certs |
| ECDH / ECDHE | Yes | No | 128-bit | Perfect forward secrecy in TLS 1.3 |
| DH / DHE | Yes | No | 128-bit (3072-bit key) | Replaced by ECDHE in modern TLS |
| Ed25519 | No | Yes | ~128-bit | SSH keys, modern PKI |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco 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 300-410 exam.