3Com 3C16476A User Guide - Page 41

Configuring VLANs 41 Figure 33 Tagged VLAN Configuration To set up the configuration shown in Figure 33, do the following: 1 Create VLAN2 on both Switch 1 and Switch 2. You need not create VLAN1 since it exists by default. 2 On Switch 1, set the ports that you want to be part of VLAN2 to Untagged. Set one port (for example, port 16) to Tagged. Click Apply. 3 On Switch 2, set the ports that you want to be part of VLAN2 to Untagged. Set one port (for example, port 8) to Tagged. Click Apply. 4 Connect the Tagged port on Switch 1 (in this example, port 16) to the Tagged port on Switch 2 (in this example, port 8). Those ports on Switch 1 that are members of VLAN2 can now communicate with those ports on Switch 2 that are members of VLAN2. Spanning Tree 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 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 bridge protocol data units (BPDUs) 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 reestablish a valid network topology.