Operation Manual – VLANH3C S7500 Series Ethernet Switches Chapter 1 VLAN Overview1-6Table 1-3 Packet processing of a Hybrid portProcessing of an incoming packetIf the packet does notcarry a VLAN tagIf the packet carries aVLAN tagProcessing of anoutgoing packetz If the port is alreadyadded to its defaultVLAN, add thedefault VLAN tag tothe packet and thenforward the packet.z If the port is notadded to its defaultVLAN, discard thepacket.z If the VLAN ID is one ofthe VLAN IDs allowedto pass through theport, receive thepacket.z If the VLAN ID is notone of the VLAN IDsallowed to pass throughthe port, discard thepacket.Send the packet if theVLAN ID is allowed to passthrough the port. Use theport hybrid vlancommand to configurewhether the port keeps orstrips the tags whensending packets of a VLAN(including the defaultVLAN).1.3 Protocol-Based VLAN1.3.1 Introduction to Protocol-Based VLANProtocol-based VLAN is also known as protocol VLAN, which is another way to classifyVLANs besides port-based VLAN. Through the protocol-based VLANs, the switch cananalyze the received un-VLAN-tagged packets on the port and match the packets withthe user-defined protocol template automatically according to different encapsulationformats and the values of specific fields. If a packet is matched, the switch will add acorresponding VLAN tag to it automatically. Thus, the data of the specific protocol isassigned automatically to the corresponding VLAN for transmission.This feature is used for binding the ToS provided in the network to VLAN to facilitatemanagement and maintenance.1.3.2 Encapsulation Format of Ethernet DataThis section introduces the common encapsulation formats of Ethernet data for you tounderstand well the procedure for the switch to identify the packet protocols.I. Ethernet II and 802.2/802.3 encapsulationIn the link layer, there are two main packet encapsulation types: Ethernet II and802.2/802.3, whose encapsulation formats are described in the following figures.Ethernet II packet:DA&SA(12) Type(2) DataFigure 1-4 Ethernet II encapsulation format802.2/802.3 packet:
