Operation Manual – VLANH3C S3100-52P Ethernet Switch Chapter 1 VLAN Overview1-7Table 1-2 Packet processing of a trunk portProcessing of an incoming packetFor an untagged packet For a tagged packetProcessing of anoutgoing packetz If the port has alreadybeen added to its defaultVLAN, tag the packetwith the default VLANtag and then forward thepacket.z If the port has not beenadded 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 passthrough the port,discard the packet.z If the VLAN ID is justthe default VLAN ID,strip off the tag andsend the packet.z If the VLAN ID is notthe default VLAN ID,keep the original tagunchanged andsend the packet.Table 1-3 Packet processing of a hybrid portProcessing of an incoming packetFor an untagged packet For a tagged packetProcessing of anoutgoing packetz If the port has alreadybeen added to itsdefault VLAN, tag thepacket with the defaultVLAN tag and thenforward the packet.z If the port has notbeen added to itsdefault VLAN, discardthe packet.z If the VLAN ID is oneof the VLAN IDsallowed to passthrough the port,receive the packet.z If the VLAN ID is notone of the VLAN IDsallowed to passthrough the port,discard the packet.Send the packet if theVLAN ID is allowed to passthrough the port. Use theport hybrid vlancommand to configurewhether the port keeps orstrips off 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. Through the protocol-based VLANs, the switch can analyze the receivedpackets carrying no VLAN tag on the port and match the packets with the user-definedprotocol template automatically according to different encapsulation formats and thevalues of specific fields. If a packet is matched, the switch will add a correspondingVLAN tag to it automatically. Thus, data of specific protocol is assigned automatically tothe corresponding VLAN for transmission.This feature is used for binding the ToS provided in the network to VLAN to facilitatemanagement and maintenance.
