Device Features

This window enables or disables these features:

• Spanning Tree Protocol (STP)
• IP Multicast (IGMP)

Using the browser interface, you can enable or disable each of the above features. By using the switch console interface, you can access and adjust individual parameters to improve the performance of these features. You can Telnet to the console interface from the Device View option under the Configuration tab.

Note: A "VLAN Selection" menu option appears only if the switch has already been configured (via the switch console interface) for multiple VLANs. If this option appears, selecting a VLAN will have an effect on IP Multicast (IGMP), but not on the Spanning Tree Protocol.

Spanning Tree

The switch uses the IEEE 802.1D Spanning Tree Protocol (STP), when enabled, to ensure that only one path at a time is active between any two nodes in the network. In networks where there is more than one physical path between any two nodes, STP ensures a single active path between them by blocking all redundant paths and retaining them as backups. If the active path shuts down, then STP automatically activates (unblocks) an available backup to serve as the new active path. The default STP setting is "Off". STP sees a port trunk as a single link, or path.

If Multiple VLANs Are Configured

Because the switch follows the 802.1Q VLAN recommendation to use single-instance spanning tree, STP operates across all switch ports instead of on a per-VLAN basis. This means that if redundant physical links exist between the switch and another 802.1Q-compliant device, all but one of these links will be blocked, regardless of whether the redundant links are in separate VLANs. However, in this case, you can use Port Trunking to prevent STP from unnecessarily blocking ports (and to improve overall network performance). For more information, refer to the Management and Configuration Guide for your switch.

To Enable STP:

1. In the Spanning Tree menu, select "On".
2. Click on the Apply Changes button.

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IP Multicast Filtering (IGMP)

In a broadcast domain (or VLAN) where IP multicast traffic is transmitted for various multimedia applications, you can use the switch to reduce unnecessary bandwidth usage on a per-port basis by enabling IGMP. When IGMP is disabled (the default), the switch forwards all IGMP traffic to all ports, which causes unnecessary bandwidth usage on ports not belonging to multicast groups. Enabling IGMP enables the switch to detect the ports to which IGMP traffic should be forwarded and to prevent IGMP traffic from going out ports where it is not needed.

The default IGMP setting is "Off". The browser interface enables or disables IGMP. For additional control options, use the switch console interface. (You can Telnet to the console interface from the Device View option under the Configuration tab.) For further information on IGMP, refer to the manual provided with the switch.

To Enable IGMP:

1. If the "VLAN Selection" menu is displayed, select the VLAN in which you want to enable IGMP.
2. In the Multicast Filtering (IGMP) menu, select "On".
3. Click on the Apply Changes button.

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