What is Layer 2 forwarding?
The process of switching frames based on MAC addresses.
What table is used in Layer 2 forwarding?
MAC address table (or CAM table).
How does a switch learn MAC addresses?
By examining the source MAC address of incoming frames.
What happens when a frame with an unknown destination MAC is received?
The switch floods the frame out all ports in the same VLAN except the one it came in on.
What happens when a frame is destined for a known MAC address?
The switch forwards the frame only out the associated port.
What is MAC address aging?
The process of removing inactive MAC addresses from the MAC table after a timeout.
What is flooding in Layer 2?
Sending frames out all ports except the source port when the destination MAC is unknown.
What is the purpose of VLANs in Layer 2 forwarding?
To segment broadcast domains and contain Layer 2 traffic within VLANs.
What is the role of the FIB in Layer 2 switching?
Layer 2 switches do not use a FIB; they use a MAC address table.
What is frame flooding used for?
To reach unknown unicast, broadcast, or multicast destinations.
What is the default MAC aging time on Cisco switches?
300 seconds.
What is a unicast frame?
A frame intended for a single MAC address.
What is a broadcast frame?
A frame intended for all hosts in the broadcast domain (FF:FF:FF:FF:FF:FF).
What is a multicast frame?
A frame intended for a group of hosts identified by a specific MAC address range.
How does Layer 2 forwarding differ from Layer 3 routing?
Layer 2 uses MAC addresses and does not decrement TTL; Layer 3 uses IP addresses and decrements TTL.
What is the result of a MAC address table overflow?
The switch may flood all frames, similar to a hub.
What is store-and-forward switching?
The switch reads the entire frame before forwarding.
What is cut-through switching?
The switch starts forwarding the frame after reading the destination MAC address.
What is fragment-free switching?
The switch reads the first 64 bytes before forwarding to avoid collision fragments.
What is the switch’s behavior when the source MAC address is already in the MAC table on a different port?
The switch updates the entry with the new port.
A switch receives a frame with a known destination MAC on the same port as the source. What does it do?
It drops the frame because it would be forwarding it back out the same port it was received on.
You see excessive flooding on a switch port. What could be a likely cause at Layer 2?
A full or unlearned MAC address table, or a topology loop without STP.
A frame enters a switch with a source MAC not in the CAM table. What does the switch do first?
It adds the source MAC and its incoming port to the CAM table.
