l2rstp
Switching > Rapid Spanning Tree
The Rapid Spanning Tree Protocol (RSTP) is implemented to support Layer 2 network designs with redundant paths.
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 performing physical network connectivity between the NSA 2400MX and another switch.
When the NSA 2400MX is booting up, ports are disabled until Spanning Tree configuration is applied. The NSA 2400MX 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 in the SonicOS management interface:
• 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 in the SonicOS management interface:
• Port Cost – Can be left in auto-mode, in which case port cost will be 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.
See the following procedures:
To configure the Bridge Settings on the Switching > Rapid Spanning Tree page, perform the following steps:
Step 1 To specify the spanning tree protocol version to use, select one of the following from the Force Version drop-down list:
• RSTP Operation – Use Rapid Spanning Tree Protocol.
• STP Only – Use the original Spanning Tree Protocol.
Step 2 To specify the priority of the root bridge, type the desired priority into the Bridge Priority field.
Step 3 To specify the Hello time, type the desired number of seconds to allow into the Hello Time (secs) field. The Hello time is the time interval between transmission of BPDUs by the root bridge. The default is 3 and the range is 1 to 10 seconds. The Hello time is communicated to other switches by including it in the BPDU.
Step 4 To specify the forward delay, type the desired number of seconds into the Forward Delay (secs) field. The forward delay is the time allowed for the listening and learning state. The default is 15 and the range is 4 to 30 seconds. The forward delay setting is communicated to other switches by including it in the BPDU.
Step 5 When finished, click Apply.
When port settings have been specified for an interface, the Port Settings table on the Switching > Rapid Spanning Tree page contains a row for that interface. A Configure icon is enabled for it unless Link Aggregation is enabled for the interface.
To configure the Port Settings on the Switching > Rapid Spanning Tree page, perform the following steps:
Step 1 Under Port Settings, click the Configure icon in the row for the interface you want to edit.
Step 2 In the Edit RSTP Settings window, select the Enable RSTP checkbox to enable Rapid Spanning Tree Protocol for this interface. Clear the checkbox to disable RSTP on this interface.
Step 3 To specify the path cost for the port, type the desired cost value into the Port Path Cost field. If left in auto-mode, the port cost will be determined based on link speed. You can also assign an arbitrary cost value or base the cost on guidelines provided by the RSTP or STP specification. The cost is higher for lower bandwidth connections. According to some guidelines, the cost of a 1 Gbps bandwidth connection would be 2, compared to the cost of 100 for a 10 Mbps connection.
Step 4 To specify the port priority, type the desired priority into the Port Priority field. A lower number indicates higher priority. Port priority is important when multiple ports are connected to the same switch and there is a possible loop. The port with the lower priority is blocked.