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Zorluk: Çok zorVLAN Configuration and Access Port Setup

A network administrator executes the following command sequence on a freshly unboxed Cisco Catalyst switch interface to connect an unmanaged host:

Switch(config)# interface FastEthernet0/12
Switch(config-if)# switchport mode access
Switch(config-if)# switchport access vlan 40

Prior to this configuration, VLAN 40 was not created in the switch VLAN database. Assuming all other interfaces remain in their default factory state, how does Cisco IOS process ingress frames from this host and manage the broadcast domain?

  1. Cisco IOS automatically creates VLAN 40 in the VLAN database, assigns FastEthernet0/12 to VLAN 40, and confines ingress broadcast frames from the host strictly within VLAN 40.Cevap
  2. B
    Cisco IOS drops all ingress untagged frames received on FastEthernet0/12 until VLAN 40 is explicitly created using the global 'vlan 40' command.
  3. C
    Cisco IOS forwards ingress broadcast traffic from FastEthernet0/12 out all active switch interfaces because uninitialized access VLANs default to forwarding across the global collision domain.
  4. D
    Cisco IOS places FastEthernet0/12 into an err-disabled state because an access port cannot be bound to a non-existent VLAN number.

Cevap

Cisco IOS automatically creates VLAN 40 in the VLAN database, assigns FastEthernet0/12 to VLAN 40, and confines ingress broadcast frames from the host strictly within VLAN 40.
When configuring an access port with 'switchport access vlan <id>', Cisco IOS checks if the specified VLAN exists in the VLAN database. If it does not exist, Cisco IOS automatically creates the VLAN in the database and assigns the interface to it. The interface then functions as an active access port within that dedicated VLAN broadcast domain.

Adım Adım Çözüm

1
Analyze the interface commands provided.
The command 'switchport mode access' sets the port to access mode, and 'switchport access vlan 40' targets VLAN 40 for access traffic.
This establishes static L2 access port membership.
2
Evaluate Cisco IOS dynamic VLAN creation behavior.
When a non-existent VLAN ID is referenced in an access port configuration, Cisco IOS automatically generates that VLAN in the local VLAN database.
Cisco Catalyst switch software automatically creates missing access VLANs to ensure seamless port assignment.
3
Determine Layer 2 broadcast domain boundaries.
Traffic received on FastEthernet0/12 is tagged internally as belonging to VLAN 40, isolating broadcast traffic to ports within VLAN 40.
Each VLAN represents a distinct Layer 2 broadcast domain.

Anahtar Kavram

Automatic VLAN Creation on Access Port Assignment
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Konular

VLAN Configuration and Access Port Setup

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