VLAN Commands 793In PBVLANs, the VLAN classification of a packet is based on its protocol (IP,IPX, NetBIOS, and so on). PBVLANs help optimize network traffic becauseprotocol-specific broadcast messages are sent only to end stations using thatprotocol. End stations do not receive unnecessary traffic, and bandwidth isused more efficiently. It is a flexible method that provides a logical groupingof users. An IP subnet or an IPX network, for example, can each be assignedits own VLAN. Additionally, protocol-based classification allows anadministrator to assign nonrouting protocols, such as NetBIOS or DECnet, tolarger VLANs than routing protocols like IPX or IP. This maximizes theefficiency gains that are possible with VLANs.In port-based VLAN classification, the Port VLAN Identifier (PVID) isassociated with the physical ports. The VLAN ID (VID) for an untaggedpacket is equal to the PVID of the port. In port-and protocol-based VLANclassifications, multiple VIDs are associated with each of the physical ports.Each VID is also associated with a protocol. The ingress rules used to classifyincoming packets include the use of the packet's protocol, in addition to thePVID, to determine the VLAN to which the packet belongs. This approachrequires one VID on each port for each protocol for which the filter is desired.IP Subnet Based VLANsThis feature allows an untagged packet to be placed in a configured VLANbased upon its IP address.MAC-Based VLANsThis feature allows an untagged packet to be placed in a configured VLANbased upon its MAC address.Private VLAN CommandsThe Dell Networking Private VLAN feature separates a regular VLAN domaininto two or more subdomains. Each subdomain is defined (represented) by aprimary VLAN and a secondary VLAN. The primary VLAN ID is the same forall subdomains that belong to a private VLAN. The secondary VLAN IDdifferentiates subdomains from each another and provides Layer 2 isolationbetween ports of the same private VLAN. There are the following types ofVLANs within a private VLAN:
