A network host sends a unicast Ethernet frame to a Layer 2 switch. The source MAC address of the frame is not currently present in the switch's MAC address table, but the destination MAC address is already mapped to an active interface. In what sequence does the switch perform operations to process and forward this frame? Arrange the switch operations in the correct chronological order from first to last.
- 1The switch receives the incoming Ethernet frame on an ingress interface.
- 2The switch inspects the frame's source MAC address and creates a new entry mapping it to the ingress interface in the MAC address table.
- 3The switch inspects the frame's destination MAC address and queries the MAC address table.
- 4The switch locates a matching entry for the destination MAC address and identifies the corresponding egress interface.
- 5The switch forwards the frame directly out the identified egress interface without flooding.
Answer
The correct sequence of switch operations is: receiving the frame on the ingress interface, examining and recording the source MAC address in the MAC address table, looking up the destination MAC address in the table, identifying the corresponding egress interface, and forwarding the unicast frame directly out that egress interface.
When an Ethernet frame arrives on a switch port, the switch first learns or updates the mapping of the frame's source MAC address to the ingress interface in its MAC address table. Next, it performs a lookup for the destination MAC address. Because the destination MAC address is already known, the switch identifies the single mapped egress interface and forwards the frame directly out that port without flooding.
Step-by-Step Solution
Key Concept
Layer 2 MAC Address Table Learning and Known Unicast Forwarding Logic