hi all,
all switches are running rapid-PVST. a VSS formed by 2x 6506-E connects to access switches via port-channel, no redundant physical link, it is like:
VSS <---port_channel--->access_switch
since some of the access port is not explicitly configured with portfast, and the device connected to it will frequently be powered on and off, which definitely will cause topology change. Will this kind of topology change cause the VLAN any temporary down, flap or jitter? Typically how fast the re-convergency will be completed? (Question 1)
And, I am really confused with "Topology Change Detection" and "Topology Change Propagation" in Understand Rapid Spanning Tree Protocol (802.1w)
"When a RSTP bridge detects a topology change, these occur:
It starts the TC While timer with a value equal to twice the hello-time for all its non-edge designated ports and its root port, if necessary.
It flushes the MAC addresses associated with all these ports."
why it will flush the MAC address associated with these non-edge ports (if configured correctly, it should be the trunk port connected to other bridge)? If the topology change occurs to the switch, what the point that the switch flush the MAC address learnt from its trunk port? (Question 2)
and,
"When a bridge receives a BPDU with the TC bit set from a neighbor, these occur:
It clears the MAC addresses learned on all its ports, except the one that receives the topology change.
It starts the TC While timer and sends BPDUs with the TC bit set on all its designated ports and root port (RSTP no longer uses the specific TCN BPDU, unless a legacy bridge needs notification)."
if a switch receives a TC BPDU, what is the point that it clears the MAC address learned on all its ports? the TC is not occuring to the switch, instead it just receives a TC BPDU indicating there is TC from another switch, why it will clear the MAC address learned on all its ports? (Question 3)
