CLI Guide

Layer 2 Switching Commands 857
Protocol Based VLANs
The main purpose of Protocol-based VLANs (PBVLANs) is to selectively
process packets based on their upper-layer protocol by setting up protocol-
based filters. Packets are bridged through user-specified ports based on their
protocol.
In PBVLANs, the VLAN classification of a packet is based on its protocol (IP,
IPX, NetBIOS, and so on). PBVLANs help optimize network traffic because
protocol-specific broadcast messages are sent only to end stations using that
protocol. End stations do not receive unnecessary traffic, and bandwidth is
used more efficiently. It is a flexible method that provides a logical grouping
of users. An IP subnet or an IPX network, for example, can each be assigned
its own VLAN. Additionally, protocol-based classification allows an
administrator to assign nonrouting protocols, such as NetBIOS or DECnet, to
larger VLANs than routing protocols like IPX or IP. This maximizes the
efficiency gains that are possible with VLANs.
In port-based VLAN classification, the Port VLAN Identifier (PVID) is
associated with the physical ports. The VLAN ID (VID) for an untagged
packet is equal to the PVID of the port. In port-and protocol-based VLAN
classifications, multiple VIDs are associated with each of the physical ports.
Each VID is also associated with a protocol. The ingress rules used to classify
incoming packets include the use of the packet's protocol, in addition to the
PVID, to determine the VLAN to which the packet belongs. This approach
requires one VID on each port for each protocol for which the filter is desired.
IP Subnet Based VLANs
This feature allows an untagged packet to be placed in a configured VLAN
based upon its IP address.
MAC-Based VLANs
This feature allows an untagged packet to be placed in a configured VLAN
based upon its MAC address.