3Com 2426-PWR, 2226-SFP, 2250-SFP manual Port Setup, Spanning Tree Setup Screen

Setup

To use spanning tree, use the Setup tab and choose Enabled from the State drop down menu, fill in the setup parameters, and click Apply.

Figure 41 Spanning Tree Setup Screen

Port Setup

This administrative tool supports the configuration of the Switch to forward, or block and discard 802.1D spanning tree BPDU packets.

Spanning tree is a bridge-based system for providing fault tolerance on networks and can be used to detect and disable network loops. The spanning tree ensures

Configuring VLANs 53

that the optimal path is maintained between spanning tree-compliant networked devices by:

■Disabling redundant paths when the main paths are operational.

■Enabling redundant paths if the main paths fail.

Spanning tree uses a distributed algorithm to select a bridging device that serves as the root of the spanning tree network. The bridging device, known as the Root Bridge, generates BPDUs (Bridge Protocol Data Units) on all ports at a regular interval, known as the Hello Time. All other spanning tree-compliant devices on the network have a designated Root Port. This is the Port nearest the Root Bridge and it is used for receiving the BPDUs initiated by the Root Bridge. If a bridge does not get a Hello BPDU after a predetermined interval, the bridge assumes that the link to the Root Bridge is down. This bridge will then initiate negotiations with other bridges to reconfigure the network to re-establish a valid network topology.

After all the bridges on the network have determined the configuration of their ports, each bridge only forwards traffic between the Root Port and the ports that are the Designated Bridge Ports for each network segment. All other ports are blocked, which means that they are prevented from forwarding traffic.

Use the Port Setup tab to configure the spanning tree settings for each port. The following options are available: