A network technician is auditing Layer 2 frame processing on a managed switch. Port 1 is an access port assigned to VLAN 30 (Engineering), Port 2 is an access port assigned to VLAN 40 (Finance), and Port 24 is configured as an 802.1Q trunk port allowing VLANs 10, 30, and 40, with Native VLAN configured as 10. A workstation connected to Port 1 sends an Ethernet broadcast frame (destination MAC `FF:FF:FF:FF:FF:FF`). Which TWO of the following statements correctly describe how the switch handles this incoming frame? (Select TWO.)
- The switch floods the broadcast frame out all active access ports assigned to VLAN 30, but does not transmit it out Port 2.Answer
- BThe switch strips any existing VLAN tags and forwards the frame out Port 24 without an 802.1Q header.
- The switch inserts an 802.1Q tag specifying VLAN ID 30 into the Ethernet frame header before forwarding it out Port 24.Answer
- DThe switch inspects the destination IP address and uses its local ARP table to route the Layer 2 broadcast directly into VLAN 40.
- EThe switch replaces the frame's source MAC address with the switch's base MAC address before egressing out Port 24.
Answer
The switch floods the broadcast frame out all active access ports assigned to VLAN 30 while excluding VLAN 40 ports, and encapsulates the frame with an 802.1Q tag specifying VLAN ID 30 when forwarding it over the trunk link.
VLANs operate as separate Layer 2 broadcast domains. Therefore, an Ethernet broadcast originating on a VLAN 30 access port is flooded only to other ports within VLAN 30 (excluding ports in VLAN 40). Additionally, when forwarding this frame out an 802.1Q trunk link where the native VLAN is set to 10, the switch must insert an 802.1Q VLAN tag (VID 30) into the frame to preserve its VLAN membership across the trunk.
Step-by-Step Solution
Key Concept
VLAN Broadcast Containment and 802.1Q Trunk Egress Tagging Logic