Examkin

Question

Difficulty: Very hardVLAN Configuration and Access Port Setup

A network administrator configures a Cisco Catalyst switch with a new VLAN and assigns an access port using the following command sequence:

Switch(config)# vlan 50
Switch(config-vlan)# name HR_Data
Switch(config-vlan)# exit
Switch(config)# interface fastEthernet 0/15
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 50

Several weeks later, another engineer executes the command 'no vlan 50' in global configuration mode to remove VLAN 50 from the switch. What is the immediate operational state and forwarding behavior of port FastEthernet 0/15 after VLAN 50 is deleted?

  1. The port remains configured for VLAN 50, but becomes inactive and drops all incoming and outgoing frames.Answer
  2. B
    The port automatically reverts its access assignment to default VLAN 1 and continues forwarding host traffic.
  3. C
    The port transitions to an error-disabled state to prevent potential native VLAN mismatch issues on adjacent links.
  4. D
    The switch automatically re-creates VLAN 50 in the VLAN database as soon as a frame is received on FastEthernet 0/15.

Answer

The port remains configured for VLAN 50, but becomes inactive and drops all incoming and outgoing frames.
When a VLAN is deleted from a Cisco switch using the global configuration command 'no vlan <id>', the switch does not modify interface-level configuration commands. Interfaces previously assigned to that VLAN retain their 'switchport access vlan <id>' setting. However, because the target VLAN no longer exists in the Layer 2 VLAN table, the switchport becomes inactive and cannot forward frames until the VLAN is re-created globally or the port is reassigned to an existing active VLAN.

Step-by-Step Solution

1
Analyze interface configuration retention upon VLAN deletion in Cisco IOS.
Removing a VLAN globally with 'no vlan <id>' removes the VLAN entry from the VLAN database (vlan.dat), but does not alter the running configuration of interfaces configured with 'switchport access vlan <id>'.
Interface configuration commands and global VLAN database definitions operate independently.
2
Determine the operational forwarding state of an interface assigned to a non-existent VLAN.
Because the assigned access VLAN no longer exists in Layer 2 forwarding tables, the switchport becomes inactive and fails to forward ingress or egress traffic for attached hosts.
A switchport cannot forward Layer 2 frames unless its configured access VLAN actively exists in the switch's VLAN database.

Key Concept

Access Port Behavior upon VLAN Deletion
Rate this question

Topics

VLAN Configuration and Access Port Setup

More questions from this topic