High CPU usage when S series switch functions as a DHCP relay agent

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When an S series switch functions as a DHCP relay agent, multiple VLANs need to be configured on the switch so that the switch can forward DHCP Request messages of clients on multiple network segments. When the switch receives a DHCP Request message from a client, it traverses all VLANs to find the VLAN ID and determine the gateway address of the client. Too large a VLAN ID uses excessive CPU resources, resulting in a high CPU usage.
In actual networking, do not allocate IP addresses on many IP network segments to clients when a switch is used as a DHCP relay agent, and fewer VLAN IDs should be used. To assign IP addresses to a large number of clients, configure multiple DHCP relay agents.

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High CPU usage when S series switch functions as a DHCP relay agent
When an S series switch functions as a DHCP relay agent, multiple VLANs need to be configured on the switch so that the switch can forward DHCP Request messages of clients on multiple network segments. When the switch receives a DHCP Request message from a client, it traverses all VLANs to find the VLAN ID and determine the gateway address of the client. Too large a VLAN ID uses excessive CPU resources, resulting in a high CPU usage. In actual networking, do not allocate IP addresses on many IP network segments to clients when a switch is used as a DHCP relay agent, and fewer VLAN IDs should be used. To assign IP addresses to a large number of clients, configure multiple DHCP relay agents.

Do S series switches support the DHCP server polling function on a DHCP relay agent
When functioning as a DHCP relay agent, the S series switch excluding the S1700 supports the DHCP server polling function on a DHCP relay agent starting from V100R006C00. By default, the DHCP server polling function on a DHCP relay agent is disabled. You can enable the DHCP server polling function on a DHCP relay agent by configuring ip relay address cycle in the system view.

Does the S series switch used as the DHCP relay agent support QinQ
On an S series switch excluding the S1700, the DHCP relay function can be configured on QinQ termination sub-interfaces.

Why clients cannot go online when S series switch functions as a DHCPv6 relay agent
A PC may fail to go online when an S series switch functions as the DHCPv6 relay agent due to the following: If the PC is directly connected to the switch, check multicast packet statistics on the interface connected to the PC. If the inbound counter is 0, the firewall of the PC may have discarded DHCPv6 Request messages. In this case, disable the firewall and obtain an IP address again.

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