FortiGate Administration Guide - FirewallShop.com

Using Spanning-Tree Protocol
Switch (FortiGate-224B only)
Monitored Ports
Port
Mode
Add/Edit
Select port and type of monitoring and then select Add/Edit.
Select the port to monitor.
Select None, Ingress, Egress or Both.
Select to add the port to the list.
Using Spanning-Tree Protocol
Spanning Tree Protocol (STP) is a Layer-2 protocol that ensures that only one
active path exists between any two network interfaces. This prevents loops, but if
there are multiple paths, it can provide redundancy to protect against link failures.
Using information exchanged amongst switches, spanning tree protocol defines a
root switch and a loop-free path from the root to each switch in the network.
Redundant data paths are blocked. If a network segment fails and a redundant
path exists, the spanning-tree algorithm activates the standby path. The network
topology is continuously recalculated and updated.
When two interfaces on a switch are part of a loop, spanning tree protocol uses
port priority and path cost settings to determine which interface is used and which
is blocked.
FortiGate-224B supports three STP modes:
STP
RSTP
PVST+
This is the traditional STP protocol defined in IEEE 802.1D-1998. In this mode,
FortiGate-224B can interoperate with other switches running traditional STP.
Rapid STP as defined in IEEE 802.1D-2004. FortiGate-224B creates a single
STP network that spans all VLANs. This is also referred to as Common Spanning
Tree (CSTP). In this mode, FortiGate-224B can interoperate with other switches
running either RSTP or traditional STP on a port-by-port basis.
RSTP is the default STP mode for FortiGate-224B.
Per-VLAN STP. FortiGate-224B creates a CSTP network that covers all VLANs
plus an STP network for each VLAN. In this mode, FortiGate-224B can
interoperate with other switches running PVST+ that are connected by access
links and 802.1Q trunks.
Configuring Spanning-Tree settings
Go to Switch > Protocols > Spanning-Tree to configure Spanning Tree settings.
Figure 122:Spanning Tree Protocol settings - STP or RSTP
FortiGate Version 3.0 MR5 Administration Guide
214 01-30005-0203-20070830