How to Identify Physical Switch Ports for Connected Devices?

N10-009 By islever Editorial Last updated

Short answer

A LLDP

Question

While troubleshooting a VoIP handset connection, a technician's laptop is able to successfully connect to network resources using the same port. The technician needs to identify the port on the switch. Which of the following should the technician use to determine the switch and port?
  1. LLDP Correct Answer
  2. IKE
  3. VLAN
  4. netstat

Key Takeaways

This question tests knowledge of Layer 2 neighbor discovery protocols, with the common trap being confusion between local operating system network utilities and physical infrastructure mapping tools.

LLDP automatically advertises device identity and port adjacency at Layer 2 to simplify physical network mapping. Community consensus strongly validates LLDP as the correct vendor-neutral solution for troubleshooting switch-to-voice endpoint connections.

Common mistake: Candidates frequently select netstat because it displays active connections, but it only reports logical TCP/UDP sockets on the local machine rather than physical switch port topology.

Expert Analysis

Why the Answer Is Correct

LLDP operates at the data link layer to broadcast device identity, capabilities, and directly connected port information across adjacent network equipment. Modern VoIP handsets leverage LLDP-MED extensions to communicate power requirements and network policies to the switch, enabling technicians to quickly trace physical connectivity. Querying the switch via LLDP provides immediate visibility into which ingress port hosts the endpoint.

Why the Other Options Are Wrong

IKE manages cryptographic key negotiation for IPsec tunnels and plays no role in physical port identification or device discovery. VLANs function as logical broadcast domains that segment traffic but lack any mechanism to report hardware adjacency or switch port mappings. netstat enumerates active transport-layer sessions and listening ports within a host operating system, rendering it completely ineffective for external infrastructure troubleshooting.

Community Comment Notes

Contributors consistently highlight LLDP’s vendor-neutral nature, noting it outperforms Cisco’s legacy CDP when dealing with third-party VoIP manufacturers. Several users recommend executing the show lldp neighbors command to instantly display connected devices alongside their corresponding switch interfaces. These practical CLI tips directly align with real-world certification scenarios and validate LLDP as the definitive troubleshooting choice.

Official Reference

https://standards.ieee.org/ieee/802.1ab/6214/revisions/

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always distinguish between host-side diagnostic commands and infrastructure discovery protocols during the exam. When a scenario emphasizes physical tracing, neighbor identification, or cross-vendor compatibility, immediately prioritize LLDP or CDP over transport-layer utilities.

Community Votes

A
100%

100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 5 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 5

  1. Intel_Geek 👍 10
    LLDP is the Link Layer Discovery Protocol, which is designed to discover neighboring network devices and their port details IKE is used for establishing VPN connections, not related VLAN logically separates network traffic, not related to identifying ports netstat views network connections and statistics, not port information
  2. nap61 👍 3 Answered A
    The Link Layer Discovery Protocol is a vendor-neutral link layer protocol used by network devices for advertising their identity, capabilities, and neighbours on a local area network based on IEEE 802 IKE - Internet Key Exchange - Not related to Switch VLAN - Not related to identify Port in the switch netstat - Identify logical ports in the computer/laptop, not in the switch
  3. chupapi_001 👍 3 Answered A
    The correct answer is A: LLDP (Link Layer Discovery Protocol) LLDP is specifically designed to help network devices advertise information about themselves and discover information about directly connected neighboring devices
  4. chrys 👍 1
    LLDP is perfect. IP phones don't necessarily support Cisco CDP, but they DO support LLDP. And you can configure both on your switch.
  5. khindinikorse 👍 2 Answered A
    show lldp

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