Why clients cannot go online when S series switch functions as a DHCPv6 relay agent

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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.

Other related questions:
Reason why the PC cannot go online when an S series switch functions as a DHCPv6 relay agent
The cause is as follows: If the PC directly connects to a switch, check whether there are statistics on multicast packets on the switch interface connected to the PC after the network cable is connected. If there are no statistics on the inbound interface, the firewall function of the PC causes DHCPv6 Request messages to be discarded. In this case, disable the firewall and then attempt to obtain IP addresses.

Clients cannot obtain IP addresses through DHCP after the DHCP relay agent is upgraded
This problem may occur on a fixed switch in the following scenario: - The switch was upgraded from V100R002/V100R003 to V100R005/V100R006. - The switch functions as a DHCP relay agent and is configured with the dhcp relay information enable command. - An authentication mechanism is enabled before the DHCP server allocates an IP address to a client. The authentication server authenticates the client based on the option 82 field. After the dhcp relay information enable command is configured on the switch, the interface name that the switch encapsulates in the DHCP option 82 field varies according to the system software version: - For V100R003 and earlier versions, a VLANIF interface name is encapsulated. - For V100R005 and later versions, a physical interface name is encapsulated. As different interface names may be encapsulated in the option 82 field before and after the upgrade, the authentication server may fail to authenticate the user based on the option 82 field. If this problem occurs, modify the user authentication configuration on the authentication server after the upgrade. To be specific, change the content of the option 82 field on the authentication server to the physical interface name, or change the user authentication policy by disabling DHCP option 82 field-based authentication.

Does the S series switch used as the DHCPv6 relay agent support PD relay
The S series switch (excluding the S1700) used as the DHCPv6 relay agent supports PD relay starting from V100R006C00. The switch can query, delete, and automatically generate routing information in the DHCPv6-PD table. You can manually configure routing information in the DHCPv6-PD table. The routing information in the DHCPv6-PD table is not lost after the switch restarts.

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.

Why cannot an AP go online when the AR functions as an AC
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