show voice port - Tecnológico de Costa Rica

8 - 6 Aironet 340 Series Bridge
Determining the Spanning Tree
All ports on a bridge, either the root port or the designated port for their
LAN, are allowed to forward packets. All others are blocked and do not
transmit or receive any data packets.
Understanding Bridge Failures
Avoiding Temporary Loops
All root and blocked ports monitor the LANs to which they are connected
and watch for configuration messages transmitted by the designated
bridge for the LAN.
The STP protocol specifies a timeout period in which these ports must
see at least one message. Each time a message is received, the timer is
restarted. If the timeout period expires, the bridge assumes the designated
bridge has failed.
The bridge will discard the saved value for the port, make the port the
designated port for that LAN, and restart sending configuration messages.
The bridge will also recalculate its values for the root bridge and
root cost based on the active ports.
Other blocked ports on the same LAN will timeout and start to transmit
messages. Eventually a new designated bridge, port, and root bridge will
be determined.
It will take a non-zero amount of time for the protocol to determine a
stable loop free topology due to the time for messages to pass from one
end of the infrastructure to the other. If the ports were allowed to forward
while the protocol was stabilizing, then temporary loops could
form.
To avoid temporary loops, ports are not allowed to go immediately from
the blocked state to the forwarding state. They must first go through a
state called listening. In this state, they may receive and transmit configuration
messages as needed but must block all data traffic. The time
spent in the listening state must be at least twice the end-to-end transmit
time of the infrastructure.