Configuring Rapid Spanning Tree

Rapid Spanning Tree Protocol allows for redundancy in case a connection goes down, while preventing loops from being formed when switches or bridges are interconnected through multiple paths.

The Rapid Spanning Tree Protocol (RSTP) is implemented to support Layer 2 network designs with redundant paths.

Dell SonicWALL’s RSTP implementation conforms to the IEEE 802.1D-2004 specification. The 802.1D specification is VLAN unaware and creates a common spanning tree (CST) that is applied to all VLANs present in the network. The RSTP implementation is backward compatible with the original 802.1D standard (STP).

RSTP supports configuration of the following objects:

•	Bridge Priority

•	Trunk ports on which RSTP is enabled/disabled

•	Port Priority

•

Port Cost

•	Hello Time

•	Forward Delay

Auto detection of non-edge ports is not supported. A non-edge port is one that is connected directly to an end-user computer such as a PC or laptop.

You can enable/disable RSTP on VLAN trunk ports only. By default, RSTP is disabled on trunk ports. You should enable the RSTP before completing physical network connectivity between the Dell SonicWALL appliance and another switch.

When the Dell SonicWALL appliance is booting up, ports are disabled until Spanning Tree configuration is applied. The appliance automatically soft-bridges the STP Bridge Protocol Data Units (BPDUs) between the ports to prevent loops when ports in the same VLAN (PortShield group or L2 Bridge mode) are connected to another switch. This allows the remote switch to detect that its ports are connected to another switch and it can automatically block certain ports.

You can view the following:

•	Current port status (forwarding, discarding, blocking)

•	Roles (root, designated, alternate, backup, disabled)

•	Current Root Bridge ID, priority, and other information

•	BPDU Rx/Tx counters

You can configure the following:

•	Port Cost – Can be left in auto-mode, in which case the port cost is determined based on link speed.

•	Port Priority – Defaults to interface number unless configured otherwise. A lower number means higher priority. Port priority is only important when ports are connected to the same switch and there is a possible loop. The port with the lower priority is blocked.

Refer to the following configuration procedures:

•	Configuring Bridge Settings

•	Configuring Port Settings