TCN |
The root port uses the
topology change notification (TCN) timer when it detects a change in
the network topology. The TCN timer stops when the topology change
timer expires or upon receipt of a topology change acknowledgement.
The default value is the same as the value for the bridge hello
timer. |
Topology change |
The topology change timer
determines the total time it takes the forwarding ports to send
configuration BPDUs. The default value for the topology change timer
depends upon the mode of the port: 802.1D
mode—The sum of the forward delay timer value (default value is
15 seconds; range of 4 to 30 seconds) and the maximum age timer
value (default value is 20 seconds; range of 6 to 40
seconds).
802.1w mode—Double the hello
timer value (default value is 4 seconds).
|
Message age |
A port uses the message age
timer to time out receiving BPDUs. When a port receives a superior
or equal BPDU, the timer restarts. When the timer expires, the port
becomes a designated port and a configuration update occurs. If the
bridge operates in 1w mode and receives an inferior BPDU, the timer
expires early. The default value is the same as the
STPD (Spanning Tree Domain) bridge max age
parameter. |
Hold |
A port uses the hold timer to
restrict the rate that successive BPDUs can be sent. The default
value is the same as the value for the bridge hello timer. |
Recent backup |
The timer starts when a port
leaves the backup role. When this timer is running, the port cannot
become a root port. The default value is double the hello time (4
seconds). |
Recent root |
The timer starts when a port
leaves the root port role. When this timer is running, another port
cannot become a root port unless the associated port is put into the
blocking state. The default value is the same as the forward delay
time. |