Question 116 of 2,152

Policy-Based Routing (PBR) →hardMultiple ChoiceObjective-mapped

300-410 Policy-Based Routing (PBR) Practice Question

This 300-410 practice question tests your understanding of policy-based routing (pbr). The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

A network engineer is troubleshooting PBR on a Cisco router where traffic from subnet 192.168.50.0/24 should be forwarded to next-hop 10.50.50.2. The route map 'PBR-50' is configured with 'match ip address 160' and 'set ip next-hop 10.50.50.2'. The engineer applies the route map to interface GigabitEthernet0/0. The engineer notices that PBR works for traffic from 192.168.50.0/24, but the router is also policy-routing traffic from other subnets that should not be affected. The engineer checks the ACL 160 and confirms it only matches 192.168.50.0/24. 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.

A
The route map has a sequence with no match condition, which matches all traffic.
Correct: If the route map has a sequence without a match condition, it matches all traffic, causing PBR to apply to unintended subnets.
B
The ACL 160 has a 'permit ip any any' statement at the end.
Why wrong: Incorrect: The engineer confirmed ACL 160 only matches 192.168.50.0/24, so there is no 'permit ip any any' at the end of the ACL.
C
The 'ip policy route-map' command is applied to multiple interfaces, and traffic from other subnets is entering those interfaces.
Why wrong: Incorrect: The problem states the route map is applied only to GigabitEthernet0/0, and traffic from other subnets would not be affected unless they enter that interface.
D
The router is using CEF switching, and PBR is applied to all traffic regardless of ACL.
Why wrong: Incorrect: CEF switching does not cause PBR to ignore ACLs; PBR uses ACLs for matching regardless of switching mode.

Full breakdown with real-world context →

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

✓

The route map has a sequence with no match condition, which matches all traffic.

The route map 'PBR-50' has a 'match ip address 160' statement, but if there is a subsequent sequence in the route map with no match condition, that sequence will match all traffic and apply the set action. This is a common misconfiguration where an additional permit sequence without a match is present, causing policy routing for all traffic. The engineer should check the route map for any sequence without a match condition.

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.

✓
The route map has a sequence with no match condition, which matches all traffic.
Why this is correct
Correct: If the route map has a sequence without a match condition, it matches all traffic, causing PBR to apply to unintended subnets.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The ACL 160 has a 'permit ip any any' statement at the end.
Why it's wrong here
Incorrect: The engineer confirmed ACL 160 only matches 192.168.50.0/24, so there is no 'permit ip any any' at the end of the ACL.
✗
The 'ip policy route-map' command is applied to multiple interfaces, and traffic from other subnets is entering those interfaces.
Why it's wrong here
Incorrect: The problem states the route map is applied only to GigabitEthernet0/0, and traffic from other subnets would not be affected unless they enter that interface.
✗
The router is using CEF switching, and PBR is applied to all traffic regardless of ACL.
Why it's wrong here
Incorrect: CEF switching does not cause PBR to ignore ACLs; PBR uses ACLs for matching regardless of switching mode.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

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.

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FAQ

Questions learners often ask

What does this 300-410 question test?

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 route map has a sequence with no match condition, which matches all traffic. — The route map 'PBR-50' has a 'match ip address 160' statement, but if there is a subsequent sequence in the route map with no match condition, that sequence will match all traffic and apply the set action. This is a common misconfiguration where an additional permit sequence without a match is present, causing policy routing for all traffic. The engineer should check the route map for any sequence without a match condition.

What should I do if I get this 300-410 question wrong?

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.

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