(Optional) Configuring Association Between ARP and DHCP Snooping

When a DHCP snooping-enabled device receives a DHCP Release message sent from a DHCP client, the device deletes the binding entry of the DHCP client. However, if a client is unexpectedly disconnected and cannot send a DHCP Release message, the device cannot immediately delete the binding entry of the DHCP client.

After association between ARP and DHCP snooping is enabled, the DHCP snooping-enabled device performs an ARP probe to detect the IP address when the ARP entry mapping an IP address ages. If the DHCP client is not detected after a specified number of probes, the device deletes the ARP entry. The device then performs an ARP probe again to detect the IP address. If the DHCP client still cannot be detected after a specified number of probes, the device deletes the binding entry of the DHCP client.

A device supports association between ARP and DHCP snooping only when the device functions as a DHCP relay agent.