Under which two circumstances would an RSTP bridge flush its CAM table? (Choose two.)

A.
Upon a port state change

B.
Upon receiving a topology change notification

C.
When transitioning from discarding to forwarding

D.
When transitioning from forwarding to discarding

E.
Only when changing from listening to discarding

F.
When CAM resources have been completely used up

Explanation:
First, the goal of RSTP is fast re-convergence. Since ports are assumed to transition to forwarding
relatively fast, simply increasing MAC address aging speed is not enough. Thus, when a topology
change is detected, RSTP instructs the bridge to flush all MAC address table entries. With
Ethernet, this process results in unconstrained flooding until the moment MAC addresses are re
learned. The bridge detecting a topology change sets the TC (Topology Change) bit in all outgoing
BPDUs and starts sending BPDUs with the TC bit set upstream through the root port as well. This
marking lasts for TCWhile=2xHelloTime seconds and allows the detecting bridge the start the
flooding process.