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Difficulty: Very hardVLAN Configuration and Access Port Setup

An administrator is troubleshooting a connectivity issue on interface GigabitEthernet1/0/5, which connects to an IP phone with a co-located workstation. The IP phone successfully registers with the Voice over IP (VoIP) server, but the workstation connected to the phone cannot communicate on the network.

The output of `show interfaces status` displays:
text
Port Name Status Vlan Duplex Speed Type
Gi1/0/5 Workstation_PC connected inactive a-full a-1000 10/100/1000BaseTX

Additionally, `show running-config interface GigabitEthernet1/0/5` yields:
text
interface GigabitEthernet1/0/5
switchport mode access
switchport access vlan 30
switchport voice vlan 200

Which condition explains why the VLAN status displays as `inactive`, and what configuration step is required to restore workstation connectivity?

  1. Access VLAN 30 does not exist in the switch VLAN database; configuring `vlan 30` in global configuration mode will activate the access VLAN and restore traffic forwarding for the workstation.Answer
  2. B
    The port experiences an 802.1Q native VLAN mismatch because VLAN 30 is not designated as native; issuing `switchport trunk native vlan 30` under interface mode will allow untagged frames to pass.
  3. C
    The access port disabled frame forwarding because PortFast is omitted; entering `spanning-tree portfast` on interface GigabitEthernet1/0/5 is required to bridge the data and voice broadcast domains.
  4. D
    The port was placed into an err-disabled state due to a security violation; executing `shutdown` followed by `no shutdown` on interface GigabitEthernet1/0/5 will clear the port state.

Answer

Access VLAN 30 does not exist in the switch VLAN database; configuring `vlan 30` in global configuration mode will activate the access VLAN and restore traffic forwarding for the workstation.
In Cisco IOS, when an interface is assigned to an access VLAN that is not currently present in the switch's VLAN database, the operational status of that VLAN on the port is set to `inactive`. As a result, untagged traffic from the attached workstation is dropped. The voice VLAN continues to operate independently because VLAN 200 exists in the database. Creating VLAN 30 using `vlan 30` in global configuration mode adds it to the VLAN database and immediately restores the port's access VLAN to active status.

Step-by-Step Solution

1
Analyze the CLI output from `show interfaces status` and `show running-config interface GigabitEthernet1/0/5`.
The interface status is `connected`, but the assigned VLAN column shows `inactive`. The interface configuration shows `switchport access vlan 30` and `switchport voice vlan 200`.
An `inactive` VLAN status in `show interfaces status` occurs specifically when a port is assigned to a VLAN ID that does not exist in the switch's VLAN database (`vlan.dat`).
2
Determine why the IP phone functions while the workstation fails.
Voice VLAN 200 exists in the VLAN database and is active, allowing tagged voice frames from the phone to forward. VLAN 30 is missing from the VLAN database, causing untagged data frames from the workstation to be dropped.
Cisco IOS handles voice and access traffic separately on multi-VLAN access ports; missing access VLAN definitions render only the data VLAN inactive.
3
Identify the required remediation command sequence.
Enter global configuration mode and create VLAN 30 using the command `vlan 30`.
Creating the VLAN in the VLAN database immediately changes the port's operational access VLAN status from `inactive` to active without modifying interface commands.

Key Concept

VLAN Database Existence and Access Port Operational States
Estimated Time:2m 0s
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Topics

VLAN Configuration and Access Port Setup

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