Question 727 of 2,152
Policy-Based Routing (PBR)mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is a misconfigured ACL 120 that ends with 'permit ip any any'. This is the most likely cause because when a route map uses a match ip address statement referencing an ACL, the ACL's permit or deny logic determines which traffic is matched for policy-based routing. If the ACL permits all traffic, either through an explicit 'permit ip any any' or an implicit permit at the end, then every packet entering the interface will match the route map's permit sequence, causing PBR to affect all traffic regardless of the intended subnet. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how route-map sequence evaluation interacts with ACL logic—a common trap is forgetting that a missing deny statement or an overly permissive ACL will cause PBR to apply broadly. Remember the memory tip: "ACL permits all, PBR answers the call" — always verify the last line of your ACL when PBR is affecting all traffic unexpectedly.

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 192.168.20.0/24 should be forwarded to next-hop 10.20.20.2. The route map 'PBR-20' is configured with 'match ip address 120' and 'set ip next-hop 10.20.20.2'. The engineer applies the route map to interface GigabitEthernet0/0. The engineer notices that PBR works for traffic from 192.168.20.0/24, but traffic from other subnets is also being forwarded to 10.20.20.2. 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.

Question 1mediummultiple choice
Review the full subnetting walkthrough →

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 permit statement with no match condition, causing all traffic to be policy-routed.

If PBR is affecting traffic from other subnets, it is likely because the route map has a permit statement without a match condition, or the ACL is misconfigured to match all traffic. The engineer should check the route map for a permit statement that matches all traffic (e.g., 'match ip address any' or missing match).

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 permit statement with no match condition, causing all traffic to be policy-routed.

    Why this is correct

    Correct because a permit statement without a match condition matches all traffic, causing PBR to apply to all packets.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    CIDR notation defines the prefix length.

  • The 'set ip next-hop' command is applied globally under the routing process.

    Why it's wrong here

    Incorrect because 'set ip next-hop' is a route-map command, not a global routing command.

  • The ACL 120 is configured with 'permit ip any any' at the end.

    Why this is correct

    Correct because if the ACL has a 'permit ip any any' statement, it will match all traffic, causing PBR to apply to all packets.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    CIDR notation defines the prefix length.

  • The route map is applied to the wrong interface, but the interface is receiving traffic from all subnets.

    Why it's wrong here

    Incorrect because if applied to the wrong interface, PBR would not work at all for the intended subnet.

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.

Trap categories for this question

  • Command / output trap

    Incorrect because 'set ip next-hop' is a route-map command, not a global routing command.

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.

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.

Related practice questions

Related 300-410 practice-question pages

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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 permit statement with no match condition, causing all traffic to be policy-routed. — If PBR is affecting traffic from other subnets, it is likely because the route map has a permit statement without a match condition, or the ACL is misconfigured to match all traffic. The engineer should check the route map for a permit statement that matches all traffic (e.g., 'match ip address any' or missing match).

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.

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Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. 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?

hard
  • A.The route map has a sequence with no match condition, which matches all traffic.
  • B.The ACL 160 has a 'permit ip any any' statement at the end.
  • C.The 'ip policy route-map' command is applied to multiple interfaces, and traffic from other subnets is entering those interfaces.
  • D.The router is using CEF switching, and PBR is applied to all traffic regardless of ACL.

Why A: If PBR is affecting traffic from other subnets despite the ACL being correct, it could be because the route map has a permit statement without a match condition, or the route map is applied to multiple interfaces. However, a common cause is that the route map has a 'match ip address' that references an ACL with a 'permit ip any any' statement at the end, or the route map has a sequence that matches all traffic. The engineer should check the route map for any sequence that does not have a match statement.

Last reviewed: Jun 18, 2026

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