Wireless Access Controller (AC and Fit AP) V200R020C10 CLI-based Configuration Guide

Configuring Traffic Optimization in Large Broadcast Domain Scenarios

Context

In enterprise and campus scenarios, a single large subnet is usually designed. Such a single large subnet simplifies VLAN configuration, roaming configuration, and fault location. However, due to the use of a large broadcast domain on this subnet, a large number of packets are replicated and sent, causing high CPU usage.

To lower the CPU usage and support large broadcast domain scenarios, you can leverage various methods such as broadcast-to-unicast conversion, unknown unicast traffic suppression, and rate limit for multicast and broadcast packets on APs.

Pre-configuration Tasks

Before configuring traffic optimization in large broadcast domain scenarios, perform the task of WLAN Service Configuration Guide.

Configuration Summary

Table 19-2 describes the traffic optimization configurations in large broadcast domain scenarios.

Table 19-2 Traffic optimization configurations in large broadcast domain scenarios

Function	Solution	How to Configure
Conversion of broadcast or multicast protocol packets (ARP, ND, and DHCP) on the air interface into unicast packets	Convert ARP, ND, and DHCP packets into unicast packets and send them to specific STAs to prevent packet duplication.	traffic-optimize bcmc unicast-send { arp \| nd \| dhcp } ^*
Discarding of broadcast or multicast protocol packets (ARP, ND, and DHCP) that failed to be converted into unicast packets on the air interface	Discard broadcast or multicast packets that failed to be converted to unicast packets on the air interface. NOTE: Before being converted into unicast packets, ND RA packets are sent to all users.	traffic-optimize bcmc unicast-send mismatch-action drop
Unknown unicast traffic suppression	Enable rate limit for unknown unicast packets on the wired and wireless sides by default. The default rate limit is 128 pps, which is configurable.	unicast-suppression auto-detect packets in the system view and AP system profile view NOTE: Ensure that intelligent flow control has been enabled for unknown unicast packets, which is enabled by default. You can disable this function using the unicast-suppression auto-detect disable command.
IGMP snooping and discarding of unknown multicast packets	IGMP snooping runs on a Layer 2 device and analyzes IGMP messages exchanged between a Layer 3 device and hosts to set up and maintain a Layer 2 multicast forwarding table. The Layer 2 device forwards multicast packets based on the Layer 2 multicast forwarding table.	igmp-snooping enable multicast drop-unknown
mDNS gateway proxy	Configure the AC as the mDNS gateway to respond to mDNS service request packets using unicast packets, reducing the packet duplication load on the AC.	See Configuring an mDNS Gateway.
Traffic rate limit	When there are a large number of broadcast, multicast, and unknown unicast packets, the CPU becomes busy processing these packets and the buffer of the packet receiving queue decreases. When the traffic rate reaches the threshold, the device automatically limits the rates of broadcast, multicast, and unknown unicast packets within the specified range.	See Configuring Rate Limit for AC Traffic and Configuring Rate Limit for AP Traffic.
Rate limit for broadcast and multicast packets on APs	To ensure normal running of network services, limit the rate of broadcast and multicast packets on APs with a proper range.	See Configuring the Rate Limit for Broadcast and Multicast Packets of APs.

To ensure the traffic optimization effect in large broadcast domain scenarios, you are advised to set the parameters to the recommended values listed in the following table.

Table 19-3 Recommended configurations in large broadcast domain scenarios

Function	Default Configuration	Recommended Configuration	Command
Conversion of broadcast or multicast protocol packets (ARP, ND, and DHCP) on the air interface into unicast packets	Enabled	Enabled	traffic-optimize bcmc unicast-send { arp \| nd \| dhcp } ^*
Discarding of broadcast or multicast protocol packets (ARP, ND, and DHCP) that failed to be converted into unicast packets on the air interface	Enabled	Enabled	traffic-optimize bcmc unicast-send mismatch-action drop
mDNS gateway proxy	Disabled	Enabled	mdns gateway enable mdns unicast-reply enable
IGMP snooping and discarding of unknown multicast packets	Disabled	Enabled	igmp-snooping enable multicast drop-unknown

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Update Date：2021-12-20

Document ID：EDOC1100195158

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