Enabling offline detection
The DHCP relay agent checks whether a user is online by learning the ARP entry. When an ARP entry is aged out, the corresponding client is considered to be offline.
With this function enabled on an interface, the DHCP relay agent removes a client's IP-to-MAC entry when it is aged out, and sends a DHCP-RELEASE message to the DHCP server to release the IP address of the client. Removing an ARP entry manually does not remove the corresponding client's IP-to-MAC binding. When the client goes offline, use the undo dhcp relay security command to remove the IP-to-MAC binding manually.
To enable offline detection:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter interface view. | interface interface-type interface-number | N/A |
3. Enable offline detection. | dhcp relay client-detect enable | Disabled by default |