Transparent Transmission of Protocol Packets in a VLAN

When a gateway device or Layer 2 switch is enabled with snooping functions such as DHCP/IGMP/MLD snooping, the device needs to parse and process protocol packets such as ARP, DHCP, and IGMP packets. That is, protocol packets received by an interface are sent to the CPU for processing. The interface sends protocol packets without differentiating VLANs. If the preceding functions are deployed, protocol packets from all VLANs are sent to the CPU for processing.

If the device works as the gateway or provides the snooping functions for only some VLANs, the device does not need to process protocol packets in other VLANs. After the protocol packets in other VLANs are sent to the CPU, the CPU needs to forward them to other devices. This mechanism is called software forwarding. Protocol packet processing in software forwarding decreases the forwarding efficiency.

To address this issue, deploy transparent transmission of protocol packets in VLANs where protocol packets do not need to be processed. This function enables the device to transparently transmit the protocol packets in the VLANs to other devices, which improves the forwarding speed and efficiency.