Specifications

212 ExtremeWare XOS 11.0 Concepts Guide
Spanning Tree Protocol
To change the existing configuration of a port in an STPD, and return the port to factory defaults, use
the following command:
unconfigure stpd <stpd_name> ports link-type <port_list>
To display detailed information about the ports in an STPD, use the following command:
show stpd <stpd_name> ports {[detail | <port_list> {detail}]}
RSTP Timers
For RSTP to rapidly recover network connectivity, RSTP requires timer expiration. RSTP derives many
of the timer values from the existing configured STP timers to meet its rapid recovery requirements
rather than relying on additional timer configurations. Table 40 describes the user-configurable timers,
and Table 41 describes the timers that are derived from other timers and not user-configurable.
Table 40: User-configurable timers
Timer Description
Hello The root bridge uses the hello timer to send out configuration BPDUs through all of
its forwarding ports at a predetermined, regular time interval. The default value is 2
seconds. The range is 1 to 10 seconds.
Forward delay A port moving from the blocking state to the forwarding state uses the forward delay
timer to transition through the listening and learning states. In RSTP, this timer
complements the rapid configuration behavior. If none of the rapid rules are in effect,
the port uses legacy STP rules to move to the forwarding state. The default is 15
seconds. The range is 4 to 30 seconds.
Table 41: Derived timers
Timer Description
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 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).