If a frame has a destination MAC address 01:00:5E:00:00:D9, how will the switch forward it?

If a frame has a destination MAC address 01:00:5E:00:00:D9, how will the switch forward it?

• A. The switch forwards it to the destination port only.
• B. The switch does not forward the frame.
• C. The switch sends the frame to a connected router because the destination MAC address is not local.
• D. The switch forwards it out all ports except the ingress port.

Answer: (D)

This is a multicast Ethernet destination address (01:00:5E indicates IPv4 multicast). In a typical Layer 2 switch, frames sent to a multicast MAC are flooded to all ports in the same VLAN except the port the frame arrived on, because the switch doesn’t know which specific devices are listening unless mechanisms like IGMP snooping are in use. So the frame will be forwarded out all ports except the ingress port. If IGMP snooping is enabled and there are subscribers to that multicast group, the switch can optimize delivery to only those ports; otherwise it floods to all, matching the stated answer.

This is a multicast Ethernet destination address (01:00:5E indicates IPv4 multicast). In a typical Layer 2 switch, frames sent to a multicast MAC are flooded to all ports in the same VLAN except the port the frame arrived on, because the switch doesn’t know which specific devices are listening unless mechanisms like IGMP snooping are in use. So the frame will be forwarded out all ports except the ingress port. If IGMP snooping is enabled and there are subscribers to that multicast group, the switch can optimize delivery to only those ports; otherwise it floods to all, matching the stated answer.