Dell PowerConnect 7048P User Manual - Page 571

Configuring VLANs 21 This chapter describes how to configure VLANs, including port-based VLANs, protocol-based VLANs, double-tagged VLANs, subnet-based VLANs, and Voice VLANs. The topics covered in this chapter include: • VLAN Overview • Default VLAN Behavior • Configuring VLANs (Web) • Configuring VLANs (CLI) • VLAN Configuration Examples VLAN Overview By default, all switchports on a PowerConnect 7000 Series switch are in the same broadcast domain. This means when one host connected to the switch broadcasts traffic, every device connected to the switch receives that broadcast. All ports in a broadcast domain also forward multicast and unknown unicast traffic to the connected host. Large broadcast domains can result in network congestion, and end users might complain that the network is slow. In addition to latency, large broadcast domains are a greater security risk since all hosts receive all broadcasts. Virtual Local Area Networks (VLANs) allow you to divide a broadcast domain into smaller, logical networks. Like a bridge, a VLAN switch forwards traffic based on the Layer 2 header, which is fast, and like a router, it partitions the network into logical segments, which provides better administration, security, and management of multicast traffic. Network administrators have many reasons for creating logical divisions, such as department or project membership. Because VLANs enable logical groupings, members do not need to be physically connected to the same switch or network segment. Some network administrators use VLANs to segregate traffic by type so that the time-sensitive traffic, like voice traffic, has Configuring VLANs 571