Question 1,663 of 2,152

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

PBR Avoiding Loops: Excluding Traffic Destined to the Router

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 matching ACL 100. The route-map is applied inbound on interface GigabitEthernet0/1. Traffic from a host on that interface is forwarded via 10.0.0.2, but the engineer notices that packets with destination IP 10.0.0.2 itself are also being redirected, causing a loop. Why does this happen?

A
The ACL 100 inadvertently matches the router's own IP address as source.
Why wrong: The issue is destination, not source.
B
PBR is applied outbound, causing packets to the router to be re-routed.
Why wrong: PBR is applied inbound; outbound application would not affect incoming packets.
C
The set ip next-hop command does not check if the next-hop is the router itself, so packets destined to the router are forwarded instead of being processed locally.
PBR overrides local delivery; packets to the router's own IP are forwarded per the policy.
D
The route-map has a default route that sends all traffic to 10.0.0.2.
Why wrong: Default routes are not part of PBR; the issue is specific to the set next-hop command.

Full breakdown with real-world context →

Quick Answer

The answer is that the set ip next-hop command does not exclude traffic destined to the router itself, so packets with a destination IP matching the next-hop address are forwarded instead of being processed locally. This happens because Policy-Based Routing (PBR) evaluates all incoming packets against the route-map before the router checks whether the destination is its own interface IP, meaning the PBR loop self-destination scenario occurs when the next-hop points back to the router. On the Cisco CCNP ENARSI 300-410 exam, this tests your understanding that PBR overrides the normal destination-based forwarding logic, and a common trap is forgetting to add a match clause to exclude traffic destined to the router’s own IP addresses. To avoid this, always include a match ip address statement that denies the router’s interface IPs, or use a prefix-list to explicitly exempt local destinations. Memory tip: "PBR doesn't check the mirror—if the next-hop is yourself, you'll loop in error."

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 set ip next-hop command does not check if the next-hop is the router itself, so packets destined to the router are forwarded instead of being processed locally.

PBR processes all incoming packets, including those destined to the router itself. If the set next-hop points to the router's own IP, packets to that IP are forwarded back out, creating a loop. The route-map should include a match clause to exclude traffic destined to the router.

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 ACL 100 inadvertently matches the router's own IP address as source.
Why it's wrong here
The issue is destination, not source.
✗
PBR is applied outbound, causing packets to the router to be re-routed.
Why it's wrong here
PBR is applied inbound; outbound application would not affect incoming packets.
✓
The set ip next-hop command does not check if the next-hop is the router itself, so packets destined to the router are forwarded instead of being processed locally.
Why this is correct
PBR overrides local delivery; packets to the router's own IP are forwarded per the policy.
Related concept
Standard ACLs match source addresses.
✗
The route-map has a default route that sends all traffic to 10.0.0.2.
Why it's wrong here
Default routes are not part of PBR; the issue is specific to the set next-hop command.

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.

Trap categories for this question

Command / output trap
Default routes are not part of PBR; the issue is specific to the set next-hop command.

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 set ip next-hop command does not check if the next-hop is the router itself, so packets destined to the router are forwarded instead of being processed locally. — PBR processes all incoming packets, including those destined to the router itself. If the set next-hop points to the router's own IP, packets to that IP are forwarded back out, creating a loop. The route-map should include a match clause to exclude traffic destined to the router.

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

What is the key concept behind this question?

Standard ACLs match source addresses.

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