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Zorluk: OrtaSwitching Concepts and VLANs

A Layer 2 switch receives an Ethernet frame on Port 2, which is an access port assigned to VLAN 15. The source MAC address 0011.AA22.BB330011.AA22.BB33 is not currently listed in the switch's CAM table. The destination MAC address 0033.CC44.DD550033.CC44.DD55 is already present in the CAM table and associated with Port 7, an access port also assigned to VLAN 15. Port 10 is an access port assigned to VLAN 30, and Port 20 is configured as an 802.1Q trunk port carrying VLAN 15 and VLAN 30.

Which TWO of the following actions will the switch perform upon processing this frame? (Select TWO.)

  1. The switch enters the source MAC address 0011.AA22.BB33 into its CAM table, associating it with Port 2 and VLAN 15.Cevap
  2. The switch forwards the frame directly out Port 7 as an untagged frame.Cevap
  3. C
    The switch floods the frame out all active interfaces in all VLANs because the source address was not previously recorded.
  4. D
    The switch drops the frame because frames entering access ports assigned to non-default VLANs must contain an 802.1Q tag.
  5. E
    The switch replicates the frame and forwards a tagged copy out trunk Port 20.

Cevap

The switch records the source MAC address 0011.AA22.BB33 mapped to Port 2 and VLAN 15 in its CAM table, and forwards the frame as an untagged Ethernet frame directly out Port 7.
When an Ethernet frame arrives at a switch, Layer 2 forwarding operations follow two distinct checks: source MAC learning and destination MAC forwarding. First, the switch checks the source MAC address. Because it is absent from the CAM table, the switch records the address 0011.AA22.BB33 associated with Port 2 in VLAN 15. Second, the switch looks up the destination MAC address 0033.CC44.DD55. Because it exists in the CAM table on Port 7 (which belongs to the same VLAN), the switch performs a microsegmentated unicast transmission directly out Port 7 as an untagged frame.

Adım Adım Çözüm

1
Analyze source MAC address processing (Ingress learning).
The source MAC address 0011.AA22.BB33 is checked against the CAM table. Since it is missing, the switch adds an entry binding 0011.AA22.BB33 to Port 2 within VLAN 15.
Layer 2 switches perform dynamic MAC address learning on incoming frames to maintain an accurate CAM table.
2
Analyze destination MAC address processing (Egress forwarding).
The destination MAC address 0033.CC44.DD55 is looked up in the CAM table and found on Port 7 in VLAN 15. The switch forwards the frame directly to Port 7.
Known unicast frames are forwarded exclusively out the specific egress interface mapped to the destination MAC address within the matching VLAN.
3
Determine frame encapsulation format on egress.
The frame is transmitted out Port 7 without an 802.1Q tag.
Access switchports communicate with end hosts using standard untagged Ethernet frames.

Anahtar Kavram

Layer 2 Switch Frame Forwarding and Dynamic MAC Learning
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Konular

Switching Concepts and VLANs

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