Need to verify VLAN assignment for a Cisco IP phone not getting an IP address? Learn why the “show vlan brief” command is essential for troubleshooting on Cisco switches, a key topic for the Cisco Certified Field Technician (CCT) exam.
Table of Contents
Question
A Cisco IP phone is connected to a switch but is not getting an IP address. What command should be used on the switch to verify VLAN assignment?
A. show interface status
B. show running-config
C. show mac address-table
D. show vlan brief
E. show arp
Answer
D. show vlan brief
Explanation
The show vlan brief command shows which VLAN a switch port is assigned to, helping verify if the phone is in the correct voice VLAN.
This command displays all VLANs configured on the switch, their status, and the ports assigned to each VLAN. It helps confirm whether the switch port connected to the IP phone is assigned to the correct voice VLAN, which is necessary for the phone to receive an IP address from the appropriate DHCP scope. If the port is not listed under the correct VLAN, the phone will not be able to communicate on the network and obtain an IP address.
- “show vlan brief” provides a summary of VLANs and their associated ports, allowing quick identification of misconfigurations or missing VLAN assignments.
- This is the most direct way to verify that the switch port is properly assigned to the required VLAN for voice traffic, which is critical for IP phone connectivity.
Other commands like “show interface status” or “show running-config” can provide additional details, but “show vlan brief” specifically shows VLAN-to-port mapping, making it the best first step for this scenario.
Cisco Certified Field Technician (CCT) certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Cisco Certified Field Technician (CCT) exam and earn Cisco Certified Field Technician (CCT) certification.