DHCP option 82 feature of the access network

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Dynamic Host Configuration Protocol (DHCP) option 82 is the DHCP Relay Agent Information Option field in a DHCP packet, and the ID of this field is 82. When a client sends a DHCP packet containing this field to the DHCP server to request for allocating an IP address, the DHCP server can determine whether the client is valid based on this field, ensuring the user access security.

Other related questions:
What cautions should be taken when configuring DHCP Option 60 and Option 43 on a Layer 2/Layer 3 network?
DHCP Option 43 and Option 60 must be configured on a Layer 3 network, while they are optional on a Layer 2 network.

ARP proxy feature of the access network
When a PC sends an Address Resolution Protocol (ARP) request to another PC, the request is processed by the access device connected to the 2 PCs. This process is called ARP proxy. ARP proxy is often used for communication between the sub virtual local area networks (VLANs) in a super VLAN.

Reasons why the Option 82 field in packets sent by other devices is replaced after the function of forcibly appending the Option 82 field is configured on S9700
S series switches support the Option 82 insertion function. The switch adds the configured Option 82 to received DHCP packets that do not contain the Option 82 field. If the packets received from other devices contain Option 82 fields, the switch deletes their original Option 82 fields and adds the configured Option 82 field to the packets.

DHCP option 60 support
S series switches (except S1700 switches) support the Option 60 field of DHCP Request packets only when they function as DHCP clients.

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