Which statement about VLAN operation on Cisco Catalyst switches is true?

D

The correct answer is D. "Unknown unicast frames are retransmitted only to the ports that belong to the same VLAN."

Explanation:

VLANs (Virtual Local Area Networks) are used to segment a network into multiple broadcast domains, which enables more efficient use of network resources and provides better network security. VLANs are implemented on Cisco Catalyst switches using either the IEEE 802.1Q trunking protocol or the Cisco Inter-Switch Link (ISL) protocol.

When a packet is received from an 802.1Q trunk, the VLAN ID can be determined from the VLAN ID field in the packet header. The VLAN ID is used to identify the VLAN to which the packet belongs. The switch uses the MAC address table to determine the destination port for the packet.

Broadcast and multicast frames are flooded to all ports in the same VLAN, except for the port on which the frame was received. This ensures that all devices in the VLAN receive the frame. Broadcast and multicast frames are not forwarded to ports in other VLANs.

Ports between switches should be configured as trunk ports to allow VLANs to span across the switches. Trunk ports carry traffic for multiple VLANs by adding a VLAN ID tag to the Ethernet frame. The receiving switch removes the VLAN ID tag and forwards the frame to the appropriate VLAN.

Unknown unicast frames are frames that have a destination MAC address that is not in the MAC address table of the switch. When a switch receives an unknown unicast frame, it floods the frame to all ports in the same VLAN, except for the port on which the frame was received. This ensures that the destination device receives the frame, if it is connected to the same VLAN. Unknown unicast frames are not forwarded to ports in other VLANs, which helps to prevent unnecessary network traffic.

In conclusion, the only statement that is true is option D, which states that "Unknown unicast frames are retransmitted only to the ports that belong to the same VLAN."