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300-410 Practice Question: A network uses PBR to load-balance traffic from…

A network uses PBR to load-balance traffic from two subnets (10.1.1.0/24 and 10.2.2.0/24) across two ISPs (next-hops 100.64.1.1 and 100.64.2.2). After a routing change, traffic from 10.1.1.0/24 is being sent to both ISPs intermittently. Router R1 shows: 'show route-map' shows the route-map with two match clauses, 'debug ip policy' shows traffic from 10.1.1.0/24 being sent to both next-hops. What is the root cause?

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 match clause that matches both subnets, causing traffic to be load-balanced across both next-hops. Use specific ACLs or separate route-map entries.

PBR route-maps can have multiple match clauses, but if the route-map does not have a 'sequence' number or if the match clauses are not mutually exclusive, traffic can match multiple clauses. In this case, the route-map likely has a match clause that matches both subnets (e.g., using a less specific ACL), causing traffic from 10.1.1.0/24 to match both clauses and be load-balanced. The solution is to ensure the ACLs in the route-map are mutually exclusive or use separate route-map entries with sequence numbers.

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 match clause that matches both subnets, causing traffic to be load-balanced across both next-hops. Use specific ACLs or separate route-map entries.

    Why this is correct

    If the ACL in the route-map matches both subnets (e.g., using a wildcard mask that is too broad), traffic from 10.1.1.0/24 can match multiple clauses, leading to load-balancing. Using specific ACLs or separate route-map entries with sequence numbers ensures each subnet is matched by only one clause.

  • The 'set ip next-hop' command is missing the 'load-balance' keyword, causing PBR to use both next-hops by default.

    Why it's wrong here

    PBR does not load-balance by default. It uses the first matching clause. The 'load-balance' keyword is not a standard PBR command; PBR uses 'set ip next-hop' with multiple next-hops for redundancy, not load-balancing.

  • The routing table on R1 has equal-cost routes to both ISPs, causing PBR to be overridden by the routing table.

    Why it's wrong here

    PBR overrides the routing table for matched traffic. The debug output shows PBR is forwarding traffic, so the routing table is not the issue.

  • The interface where PBR is applied is in a VRF, causing the route-map to be applied incorrectly.

    Why it's wrong here

    If the interface were in a VRF, the PBR configuration would need to be VRF-aware, but the symptom is about load-balancing, not VRF issues.

Visual reference

Source Router + ACL permit 10.0.0.0/8 deny any Server 10.0.0.5 ✓ 192.168.1.1 ✗ dropped ACLs evaluate top-down; first match wins — implicit deny all at end

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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.