CCNP Infrastructure Practice Question
A network administrator is deploying a new Cisco Catalyst switch in a data center. The switch must support a protocol that allows multiple physical links to be bundled into a single logical link, providing increased bandwidth and redundancy. The administrator wants to ensure that the protocol can dynamically negotiate the bundle formation with the connected device. Which protocol should be configured?
⚠ Common exam trap
Many exam-takers confuse link aggregation protocols with loop prevention or link monitoring protocols, or assuming PAgP is universally supported.
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
✓
Link Aggregation Control Protocol (LACP)
LACP is the IEEE standard for dynamic link aggregation, allowing switches from different vendors to negotiate an EtherChannel. It bundles multiple physical links into one logical link for increased bandwidth and redundancy. PAgP is Cisco-proprietary, while UDLD and STP serve entirely different purposes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
UniDirectional Link Detection (UDLD)
Why it's wrong here
UDLD is a Layer 2 protocol that detects unidirectional links and can disable ports to prevent loops. It does not bundle links or provide increased bandwidth. While it can complement EtherChannel by detecting failures, it does not perform link aggregation itself.
- ✓
Link Aggregation Control Protocol (LACP)
Why this is correct
LACP is an IEEE 802.3ad standard protocol that dynamically negotiates EtherChannel formation between devices from different vendors. It provides increased bandwidth and redundancy by bundling multiple physical links into a single logical link. This meets the requirement for dynamic negotiation and interoperability.
- ✗
Spanning Tree Protocol (STP)
Why it's wrong here
STP prevents Layer 2 loops by blocking redundant ports. It does not aggregate links into a single logical link; in fact, STP would typically block redundant links unless they are bundled in an EtherChannel. STP does not provide bandwidth aggregation or dynamic negotiation of bundles.
- ✗
Port Aggregation Protocol (PAgP)
Why it's wrong here
PAgP is a Cisco-proprietary protocol that dynamically negotiates EtherChannel formation. However, it is not supported on all devices, especially non-Cisco equipment, and the scenario does not specify that the connected device is Cisco. LACP is the standard-based alternative that provides broader compatibility.
Visual reference
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 350-401 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 350-401 exam.