Allied Telesis 2.6.1 manual Spanning Tree and Rapid Spanning Tree Port States

Layer 2 Switching 87

A spanning tree running in standard mode can take up to one minute to rebuild after a topology or configuration change. The Rapid Spanning Tree algorithm provides for a more rapid recovery of connectivity following the failure of a bridge, bridge port, or a LAN.

For information about RSTP see the Rapid Mode Spanning Tree Types section,

Switch chapter in the Rapier Switch Software Reference.

Spanning Tree and Rapid Spanning Tree Port States

If STP is running in STANDARD mode, then each port can be in one of five Spanning Tree states, and one of two switch states. If STP is running in RAPID mode, then each port can be in one of four states. The state of a switch port is taken into account by STP. To be involved in STP negotiations, STP must be enabled on the switch, the port must be enabled on the switch, and enabled for the STP it belongs to.

The Spanning Tree states (see Table 16) affect the behaviour of ports whose switch state is enabled.

Table 16: Spanning tree port states .

State	Meaning
DISABLED	STP operations are disabled on the port. The port can still
	switch if its switch state is enabled.
LISTENING	The port is enabled for receiving frames only.
LEARNING	The port is enabled for receiving frames only, and the
	Learning Process can add new source address information
	to the Forwarding Database.
FORWARDING	The normal state for a switch port. The Forwarding Process
	and the Spanning Tree entity are enabled for transmit and
	receive operations on the port.
BLOCKING	The Spanning Tree entity has disabled the Forwarding
	process for transmit and receive operations on the port, but
	the Spanning Tree entity itself remains enabled for transmit
	and receive operations on the port.

Table 17: Rapid Spanning Tree port states .

State	Meaning
DISABLED	STP operations are disabled on the port.
DISCARDING	The port does not participate in frame relay. The forwarding
	process discards received frames and does not submit
	forwarded frames for transmission.
LEARNING	The port is enabled for receiving frames only, and the
	Learning Process can add new source address information
	to the Forwarding Database. The port does not forward any
	frames.
FORWARDING	The normal state for a switch port. The Forwarding Process
	and the Spanning Tree entity are enabled for transmit and
	receive operations on the port.

Software Release 2.6.1 C613-02039-00 REV A