Dell PowerConnect 5548 User Guide - Page 21

forwarded. Non-VoIP traffic is dropped from the Voice VLAN in Auto-Voice VLAN Secure mode. Voice VLAN also provides QoS to VoIP, ensuring that the quality of voice does not deteriorate if the IP traffic is received unevenly. For more information, see "Voice VLAN" on page 491. Guest VLAN Guest VLAN provides limited network access to unauthorized ports. If a port is denied network access via port-based authorization, but the Guest VLAN is enabled, the port receives limited network access through the Guest VLAN. For more information, see "Dot1x Authentication" on page 127. Private VLAN The Private VLAN feature provides Layer 2 isolation between ports that share the same Broadcast domain, or in other words, it creates a point-tomultipoint Broadcast domain. The ports can be located anywhere in the Layer 2 network (compared to the Protected Ports feature, where the ports must be in the same stack). For more information, see "Private VLAN" on page 487. Multicast TV VLAN The Multicast TV VLAN feature provides the ability to supply multicast transmissions to Layer 2-isolated subscribers, without replicating the multicast transmissions for each subscriber VLAN. The subscribers are the only receivers of the multicast transmissions. For more information, see "Multicast TV VLAN" on page 527. Spanning Tree Protocol Features Spanning Tree Protocol (STP) 802.1d Spanning tree is a standard Layer 2 switch requirement that enables bridges to automatically prevent and resolve Layer 2 forwarding loops. Switches exchange configuration messages using specifically-formatted frames, and selectively enable and disable forwarding on ports. For more information, see "Spanning Tree" on page 428. Dell PowerConnect 55xx Systems User Guide 21