The answer is that the interface needs the 'ip route-cache policy' command to enable CEF support for PBR. This is because PBR and CEF interact in a specific way: by default, PBR is processed in software through process switching, but when CEF is enabled globally, CEF-switched packets bypass policy routing entirely unless the interface is explicitly configured to participate. The 'ip route-cache policy' command forces CEF to consult the route-map before forwarding, ensuring that policy-based routing is applied to CEF-switched traffic. On the Cisco CCNP ENARSI 300-410 exam, this is a classic trap—candidates often assume that enabling 'ip cef' globally is sufficient, but they forget the per-interface command that bridges PBR and CEF. The exam tests your understanding that CEF’s default behavior is to ignore PBR, making this a common misconfiguration scenario. Memory tip: think “CEF skips PBR without the policy key”—the interface command is the key that unlocks CEF’s cooperation with policy routing.
300-410 Policy-Based Routing (PBR) Practice Question
This 300-410 practice question tests your understanding of policy-based routing (pbr). 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.
An engineer configures PBR with a route-map that sets the next-hop to 10.0.0.2 for traffic from subnet 192.168.1.0/24. The route-map is applied inbound on interface GigabitEthernet0/0. The engineer also enables 'ip cef' globally. Traffic from 192.168.1.0/24 is not being policy-routed; instead, it follows the routing table. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
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
✓
The interface needs the 'ip route-cache policy' command to enable CEF support for PBR.
PBR and CEF interact in a specific way: PBR is processed in software (process switching) by default, but CEF-switched packets bypass PBR unless 'ip route-cache policy' is enabled on the interface. Without this command, CEF fast-switches packets, ignoring PBR.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
CEF is disabled globally, causing PBR to fail.
Why it's wrong here
CEF is enabled; disabling it would force process switching, which supports PBR.
✓
The interface needs the 'ip route-cache policy' command to enable CEF support for PBR.
Why this is correct
CEF fast-switching bypasses PBR unless policy routing is explicitly enabled in CEF.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
The route-map is missing a 'set interface' command.
Why it's wrong here
PBR can use set ip next-hop; set interface is not required.
✗
The ACL in the route-map is using a named ACL instead of a numbered one.
Why it's wrong here
Named ACLs work fine with PBR.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
Policy-Based Routing (PBR) — This question tests Policy-Based Routing (PBR) — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The interface needs the 'ip route-cache policy' command to enable CEF support for PBR. — PBR and CEF interact in a specific way: PBR is processed in software (process switching) by default, but CEF-switched packets bypass PBR unless 'ip route-cache policy' is enabled on the interface. Without this command, CEF fast-switches packets, ignoring PBR.
What should I do if I get this 300-410 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 300-410 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.