SMC Networks ElliteConnect 2.4GHz/5GHz - Manual (Page 124)

System Configuration
6-48
device (except for the root device) which incurs the lowest path
cost when forwarding a packet from that device to the root device.
Then it selects a designated bridging device from each LAN
which incurs the lowest path cost when forwarding a packet from
that LAN to the root device. All ports connected to designated
bridging devices are assigned as designated ports. After
determining the lowest cost spanning tree, it enables all root ports
and designated ports, and disables all other ports. Network
packets are therefore only forwarded between root ports and
designated ports, eliminating any possible network loops.
Once a stable network topology has been established, all bridges
listen for Hello BPDUs (Bridge Protocol Data Units) transmitted
from the root bridge. If a bridge does not get a Hello BPDU after a
predefined interval (Maximum Age), the bridge assumes that the
link to the root bridge is down. This bridge will then initiate
negotiations with other bridges to reconfigure the network to
reestablish a valid network topology.