141Enabling client offline detection on the DHCP relay agentThe client offline detection on the DHCP relay agent detects the user online status based on the ARPentry aging. When an ARP entry ages out, the DHCP client offline detection feature deletes the relayentry for the IP address and sends a RELEASE message to the DHCP server.The feature does not function if an ARP entry is manually deleted.To enable client offline detection on the DHCP relay agent:Step Command Remarks1. Enter system view. system-view N/A2. Enable the relay agent torecord relay entries.dhcp relayclient-information recordBy default, the relay agent does notrecord relay entries.Without relay entries, client offlinedetection cannot function correctly.3. Enter interface view. interface interface-typeinterface-number N/A4. Enable the DHCP relay agent. dhcp select relayBy default, when DHCP is enabled,an interface operates in the DHCPserver mode.5. Enable client offline detection. dhcp client-detect By default, client offline detection isdisabled on the DHCP relay agent.Configuring the DHCP relay agent to release anIP addressConfigure the relay agent to release the IP address for a relay entry. The relay agent sends aDHCP-RELEASE message to the server and meanwhile deletes the relay entry. Upon receiving theDHCP-RELEASE message, the DHCP server releases the IP address.To configure the DHCP relay agent to release an IP address:Step Command Remarks1. Enter system view. system-view N/A2. Configure the DHCP relayagent to release an IPaddress.dhcp relay release ip ip-address[ vpn-instancevpn-instance-name ]This command can release onlythe IP addresses in the recordedrelay entries.Configuring Option 82To support Option 82, you must perform related configuration on both the DHCP server and relayagent. For DHCP server Option 82 configuration, see "Enabling handling of Option 82."To configure Option 82:Step Command Remarks1. Enter system view. system-view N/A
