To support a DHCP-based address assignment in a Layer 2 aggregation network, the 7210 SAS supports DHCPv4 snooping. The 7210 SAS can copy packets designated to the standard UDP port for DHCP (port 67) to its control plane for inspection, this process is called DHCPv4 snooping.
DHCPv4 snooping can be performed in two directions:
From the client to the DHCP server (Discover or Request messages) to insert Option 82 information. For these applications, DHCPv4 snooping must be enabled on the SAP toward the subscriber.
From the DHCP server (ACK messages), to remove the Option 82 field toward the client. For these applications, DHCPv4 snooping must be enabled on both the SAP toward the network and the SAP toward the subscriber.