mediumMultiple Choice
300-410 Practice Question: Runs the following command to verify IPv6 traffic…
A network engineer runs the following command to verify IPv6 traffic filtering with logging:
R1# show logging | include FILTER *Mar 1 00:04:56.789: %IPV6_ACL-6-ACCESSLOGDP: list FILTER denied tcp 2001:DB8:2::1(12345) -> 2001:DB8:3::1(80), 1 packet
What does this output indicate?
⚠ Common exam trap
Cisco often tests the ability to distinguish between ACL deny/permit actions in log messages, where the trap is that candidates misread 'denied' as 'permitted' or confuse ACL logging with other features like uRPF or interface statistics.
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
✓
A TCP packet from 2001:DB8:2::1 to destination 2001:DB8:3::1 port 80 was denied by the access list.
The log message shows an IPv6 ACL (named FILTER) logging a denied TCP packet from source 2001:DB8:2::1 port 12345 to destination 2001:DB8:3::1 port 80. The keyword 'denied' in the log entry confirms the packet was blocked by the access list, making option A correct.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A TCP packet from 2001:DB8:2::1 to destination 2001:DB8:3::1 port 80 was denied by the access list.
Why this is correct
The log entry confirms the IPv6 access list named FILTER matched and dropped a TCP segment, evidenced by the ACCESSLOGDP message and "denied" keyword. Source 2001:DB8:2::1 port 12345 to destination 2001:DB8:3::1 port 80 satisfies the stem's requirement to verify filtering with logging, proving the ACL denies rather than permits.
- ✗
A TCP packet was permitted by the access list.
Why it's wrong here
The log line states denied, and the %IPV6_ACL-6-ACCESSLOGDP message is generated by a deny statement with logging enabled, so the packet was dropped, not permitted. A permit entry with log would produce an ACCESSLOGP message instead.
- ✗
The access list is not applied to any interface.
Why it's wrong here
The log entry proves the ACL is applied and matching traffic: a deny entry with the ACCESSLOGDP message only generates when packets traverse an interface bound to that list. The option confuses absence of a hit counter with absence of application. An unapplied ACL would be the answer if no log entries appeared despite matching traffic.
- ✗
The packet was dropped due to uRPF.
Why it's wrong here
The message is an IPv6 ACL deny log, not a uRPF drop, which would be reported by unicast RPF counters or a different syslog facility. The named list FILTER and ACCESSLOGDP identifier point to an explicit ACL deny entry.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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