dhcp relay release

Function

The dhcp relay release command configures a DHCP relay agent to send a release message to a DHCP server for releasing the IP address assigned to a DHCP client.

Format

In the system view:

dhcp relay release client-ip-address mac-address [ vpn-instance vpn-instance-name ] [ server-ip-address ]

In the interface view:

dhcp relay release client-ip-address mac-address [ server-ip-address ]

Parameters

Parameter	Description	Value
client-ip-address	Specifies the IP address of a DHCP client.	The value is in dotted decimal notation.
mac-address	Specifies the MAC address of a DHCP client.	The value is in H-H-H format. H is a hexadecimal number of 1 to 4 digits.
server-ip-address	Specifies the IP address of a DHCP server. If this parameter is specified, a DHCP relay agent sends a release message to the specified DHCP server for releasing the IP address assigned to a DHCP client.	The value is in dotted decimal notation.
vpn-instance vpn-instance-name	Specifies the name of the VPN instance to which the specified DHCP server releasing IP addresses belongs.	The value must be an existing VPN instance name.

Views

Interface view, system view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

This command applies to DHCP relay agents. In some situations, for example, a user is forced to go offline, the user's IP address is no longer used. However, the user cannot access the network, and will not send a DHCP release message to the DHCP server to release the IP address assigned by the DHCP server. Before the IP address lease expires, the DHCP server will not assign the user's IP address to another client, wasting IP addresses. In this case, you can run the dhcp relay release command to configure a DHCP relay agent to send a DHCP release message to the DHCP server. After receiving the message, the DHCP server sets the status of the IP address to idle. The DHCP server then can assign the released IP address to another client.

If a DHCP server address is specified, the DHCP relay agent sends an address release request only to the specified DHCP server. If no DHCP server address is specified, the following situations occur:

When the dhcp relay release command is run in the system view, the DHCP relay agent sends an address release request to DHCP servers on all the interfaces working in DHCP relay mode.
When the dhcp relay release command is run in the interface view, the DHCP relay agent sends an address release request to all DHCP servers on the VLANIF interface.

Precautions

The dhcp relay release command only releases the IP addresses dynamically assigned by DHCP servers.

When multiple DHCP relay agents are connected between the DHCP client and server, this command must be executed on the first DHCP relay agent.

Example

# Configure a DHCP relay agent to send a release message to the DHCP server at 10.1.1.1 for releasing the IP address 192.168.1.1 assigned to the DHCP client whose MAC address is 0050-ba34-2000.

<HUAWEI> system-view
[HUAWEI] dhcp relay release 192.168.1.1 0050-ba34-2000 10.1.1.1