Question 1,612 of 2,152

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

PBR Route-Map Implicit Deny: Preventing Dropped Traffic

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.

A router is configured with PBR using a route-map that sets the next-hop to 192.168.2.1 for traffic matching ACL 101. The engineer also configures 'ip route 0.0.0.0 0.0.0.0 192.168.1.1' as a default route. Traffic that matches ACL 101 is correctly forwarded to 192.168.2.1, but traffic that does not match ACL 101 is dropped instead of using the default route. What is the most likely explanation?

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 an implicit deny at the end, so unmatched traffic is dropped.
Route-maps have an implicit deny; unmatched packets are discarded unless a permit sequence with no match is added.
B
The default route is not installed in the routing table due to administrative distance.
Why wrong: The default route is present, but PBR overrides it for matched traffic; unmatched traffic should fall back to routing.
C
The ACL 101 is blocking all other traffic.
Why wrong: ACLs only define match criteria; they do not block traffic in PBR.
D
The 'ip policy route-map' command is applied outbound, causing unmatched traffic to be dropped.
Why wrong: PBR is applied inbound; outbound application would not affect incoming packets.

Full breakdown with real-world context →

Quick Answer

The answer is the route-map’s implicit deny at the end of the PBR configuration, which drops traffic that does not match ACL 101. When a route-map is applied for policy-based routing, any unmatched traffic hits the implicit deny statement and is discarded, regardless of any configured static default route. This happens because PBR overrides the routing table for matched traffic, but for non-matched traffic, the route-map’s default action is to deny, so the router never consults the global routing table. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how route-map sequence numbers and permit/deny logic interact with PBR; a common trap is assuming a static default route will catch unmatched traffic. To prevent dropped traffic, you must add a permit statement with no match clause at the end of the route-map, which allows normal routing to take over. Memory tip: “No match, no catch—add a permit to let the default route dispatch.”

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 an implicit deny at the end, so unmatched traffic is dropped.

PBR with a route-map that does not have a default action (e.g., 'set ip default next-hop' or an implicit permit) will drop non-matching traffic by default. The route-map must include a permit statement with no match to allow normal routing for unmatched traffic.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 an implicit deny at the end, so unmatched traffic is dropped.
Why this is correct
Route-maps have an implicit deny; unmatched packets are discarded unless a permit sequence with no match is added.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The default route is not installed in the routing table due to administrative distance.
Why it's wrong here
The default route is present, but PBR overrides it for matched traffic; unmatched traffic should fall back to routing.
✗
The ACL 101 is blocking all other traffic.
Why it's wrong here
ACLs only define match criteria; they do not block traffic in PBR.
✗
The 'ip policy route-map' command is applied outbound, causing unmatched traffic to be dropped.
Why it's wrong here
PBR is applied inbound; outbound application would not affect incoming packets.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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 ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related 300-410 ACL questions on filtering logic and placement.

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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) — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: The route-map has an implicit deny at the end, so unmatched traffic is dropped. — PBR with a route-map that does not have a default action (e.g., 'set ip default next-hop' or an implicit permit) will drop non-matching traffic by default. The route-map must include a permit statement with no match to allow normal routing for unmatched traffic.

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?

Standard ACLs match source addresses.

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