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Zorluk: OrtaSwitching Concepts and VLANs

A network administrator is evaluating the behavior of a Layer 2 switch configured with two isolated VLANs: VLAN 10 (Sales) and VLAN 20 (Engineering). Host A, connected to a port on VLAN 10, sends a broadcast frame onto the network. Almost simultaneously, Host B, also on VLAN 10, transmits a unicast frame addressed to Host C (on VLAN 10), but Host C's MAC address is not currently listed in the switch's CAM table. Which of the following statements accurately describe how the Layer 2 switch processes these frames? (Select TWO)

  1. The switch forwards the broadcast frame from Host A out all active ports assigned to VLAN 10 except the ingress port, but suppresses transmission to VLAN 20 ports.Cevap
  2. The switch floods the unicast frame from Host B out all active member ports of VLAN 10 except the ingress port because the destination MAC address is unknown.Cevap
  3. C
    The switch forwards the broadcast frame from Host A across all active ports on both VLAN 10 and VLAN 20 because broadcast traffic spans the entire physical switch by default.
  4. D
    The switch strips the Layer 2 frame header and re-encapsulates Host A's broadcast payload into a Layer 3 packet prior to forwarding it across ports.
  5. E
    The switch drops the unicast frame from Host B immediately because frames with unknown destination MAC addresses are discarded until a static entry is manually added to the CAM table.

Cevap

The switch forwards the broadcast frame from Host A out all active member ports of VLAN 10 except the receiving port, while isolating it from VLAN 20. In addition, because Host C's MAC address is unknown in the CAM table, the switch performs unknown unicast flooding by transmitting Host B's frame out all ports belonging to VLAN 10 except the ingress port.
VLANs create separate Layer 2 broadcast domains, meaning a broadcast frame originating on VLAN 10 will be forwarded out all active ports assigned to VLAN 10 (except the receiving port) but will never cross over to ports on VLAN 20. Furthermore, when a switch receives a unicast frame whose destination MAC address is not listed in the CAM table, it performs unknown unicast flooding, transmitting the frame to all active ports within that frame's VLAN except the ingress port.

Adım Adım Çözüm

1
Analyze the broadcast domain boundaries for Host A's broadcast frame.
VLANs define logical Layer 2 broadcast domains. Broadcast traffic originating in VLAN 10 is flooded to all active ports assigned to VLAN 10 (excluding the receiving port) and blocked from crossing into VLAN 20.
Layer 2 switches do not forward broadcast traffic across different VLAN boundaries.
2
Analyze switch forwarding behavior for Host B's unicast frame with an unlearned destination MAC address.
The switch looks up Host C's destination MAC address in its CAM table. Finding no match, it performs unknown unicast flooding within VLAN 10.
Unknown unicast traffic is flooded to all ports in the source VLAN except the port of entry so the intended recipient receives the frame and can reply, allowing the switch to learn its MAC address.

Anahtar Kavram

VLAN Broadcast Domain Boundaries and Unknown Unicast Flooding Mechanics
Tahmini Süre:1m 30s
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Konular

Switching Concepts and VLANs

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