Question

Difficulty: Very hardVLAN Configuration and Access Port Setup

A network engineer is configuring interface GigabitEthernet1/0/10 on a Cisco Catalyst switch to connect a single end-user workstation. VLAN 75 ('FINANCE') has not yet been created in global configuration mode. The engineer enters the following CLI commands:

Switch(config)# interface gigabitethernet1/0/10
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 75

Which two statements accurately describe the resulting switch behavior and interface operation? (Select two.)

  1. The switch automatically creates VLAN 75 in the VLAN database and assigns interface GigabitEthernet1/0/10 to VLAN 75.Answer
  2. Frames transmitted out interface GigabitEthernet1/0/10 toward the connected workstation will be untagged standard Ethernet frames.Answer
  3. C
    Interface GigabitEthernet1/0/10 is placed into an inactive state and drops all traffic until the 'vlan 75' command is manually executed in global configuration mode.
  4. D
    The interface automatically negotiates an 802.1Q trunk connection using VLAN 75 as the native VLAN because the VLAN was created dynamically.

Answer

The switch automatically creates VLAN 75 in the VLAN database and assigns the interface to it, and frames transmitted out interface GigabitEthernet1/0/10 toward the workstation are untagged standard Ethernet frames.
Assigning an interface to a VLAN that does not yet exist using 'switchport access vlan' prompts Cisco IOS to automatically create the VLAN in the switch database. Additionally, ports configured with 'switchport mode access' operate exclusively as untagged ports for that single VLAN when transmitting traffic to attached end-user devices.

Step-by-Step Solution

1
Analyze the Cisco IOS dynamic behavior when assigning an interface to a missing VLAN.
Cisco IOS automatically instantiates VLAN 75 in the switch VLAN database.
Automatic creation of missing VLANs is standard Cisco IOS software behavior during access port VLAN assignment.
2
Analyze frame encapsulation on a statically assigned access port.
The port strips any internal VLAN tags before transmitting frames out to the workstation.
Access ports belong to only one VLAN and send standard untagged 802.3 frames to host endpoints.

Key Concept

Cisco IOS Dynamic VLAN Creation and Access Port Framing Mechanics
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