Chapter 2: Bridging Configuration Guide2 - 2SSR User Reference Manualfewer table entries while flow-based bridging provides tighter management andcontrol over bridged traffic.VLAN OverviewVirtual LANs (VLANs) are a means of dividing a physical network into several logical(virtual) LANs. The division can be done on the basis of various criteria, giving riseto different types of VLANs. For example, the simplest type of VLANs is the port-based VLAN. Port-based VLANs divide a network into a number of VLANs byassigning a VLAN to each port of a switching device. Then, any traffic received on agiven port of a switch belongs to the VLAN associated with that port.The primary use of VLANs is for broadcast containment. A layer-2 (L2) broadcastframe is normally transmitted all over a bridged network. By dividing the network intoVLANs, the range of a broadcast is limited, i.e., the broadcast frame is transmittedonly to the VLAN to which it belongs. This reduces the broadcast traffic on a networkby an appreciable factor.The type of VLAN depends upon one criterion: how a received frame is classified asbelonging to a particular VLAN. VLANs can be categorized into the following types:1. Port based2. MAC address based3. Protocol based4. Subnet based5. Multicast based6. Policy basedDetailed information about these types of VLANs is beyond the scope of this manual.Each type of VLAN is briefly explained in the following subsections.Port-based VLANsPorts of L2 devices (switches, bridges) are assigned to VLANs. Any traffic receivedby a port is classified as belonging to the VLAN to which the port belongs. Forexample, if ports 1, 2, and 3 belong to the VLAN named “Marketing”, then a broadcastframe received by port 1 is transmitted on ports 2 and 3. It is not transmitted on anyother port.MAC-address-based VLANsIn this type of VLAN, each switch (or a central VLAN information server) keeps trackof all MAC addresses in a network and maps them to VLANs, based on information
