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notifies the network. Both RSTP and STP flush unwanted learned addresses from the filtering
database.
In STP, the port states are Blocking, Listening, Learning, Forwarding.
In RSTP, the port states are Discarding, Learning, and Forwarding.
Note
: In this document, “STP” refers to both STP and RSTP.
STP Terminology
The root bridge is the base of the spanning tree.
Path cost is the cost of transmitting a frame onto a LAN through that port. The
recommended cost is assigned according to the speed of the link to which a port is
attached. The slower the media, the higher the cost.
On each bridge, the bridge communicates with the root through the root port. The root
port is the port on this Switch with the lowest path cost to the root (the root path cost).
If there is no root port, then this Switch has been accepted as the root bridge of the
spanning tree network.
For each LAN segment, a designated bridge is selected. This bridge has the lowest cost
to the root among the bridges connected to the LAN.
Forward Time (Forward Delay):
This is the maximum time (in seconds) the Switch will wait before changing states. This
delay is required because every switch must receive information about topology changes
before it starts to forward frames. In addition, each port needs time to listen for conflicting
information that would make it return to a blocking state; otherwise, temporary data loops
might result. The allowed range is 4 to 30 seconds.
Max Age:
This is the maximum time (in seconds) the Switch can wait without receiving a BPDU
before attempting to reconfigure. All Switch ports (except for designated ports) should
receive BPDUs at regular intervals. Any port that age out STP information (provided in the
last BPDU) becomes the designated port for the attached LAN. If it is a root port, a new
root port is selected from among the Switch ports attached to the network. The allowed
range is 6 to 40 seconds.
Hello Time:
This is the time interval in seconds between BPDU (Bridge Protocol Data Units)
configuration message generations by the root switch. The allowed range is 1 to 10 seconds.