Configure DHCP Delay

By using a DHCP relay agent, the DHCP clients on a local area network (LAN) can communicate with the DHCP servers on other network segments, and obtain IP addresses from them. The DHCP clientson different network segments can also use one DHCP server. This reduces costs and achieves centralized device management.

Context

Before configuring the DHCP relay function, you must configure DHCP servers.
DHCP relay is introduced to transmit packets between DHCP clients and a DHCP server that are on different network segments. A DHCP relay agent can transparently transmit DHCP broadcast packets between DHCP clients and a DHCP server that are on different network segments.
In applications, the DHCP relay function is generally implemented on a VLANIF interface of a switch. This interface needs to be configured with an IP relay address to specify the DHCP server. An IP relay address refers to the IP address of the DHCP server specified on the DHCP relay agent. After the DHCP relay function is enabled on an interface, the DHCP broadcast packets received on the interface are sent to the specified server.
If no DHCP server is configured on a network, the DHCP relay function can be enabled on a switch. In this manner, the DHCP Request packet from clients can be transmitted to the DHCP server on another network through the DHCP relay agent. To enable clients to obtain IP addresses, the DHCP server must use a global address pool. That is, the interface of the server connected to the DHCP relay agent cannot be configured with any address pool.

Procedure

Query DHCP relay information.
1. Choose Service Management > DHCP > Configure DHCP Delay in the navigation tree to open the Configure DHCP Delay page.
2. Set the search criteria.
3. Click Query to display all matching records.

Configure DHCP relay.

Choose Service Management > DHCP > Configure DHCP Delay in the navigation tree to open the Configure DHCP Delay page.

Select a record and click Configure to open the Configure DHCP Relay page.

Table 1 describes the parameters on the Configure DHCP Relay page.

**Table 1** Configure DHCP Relay
Parameter	Description
VLANIF Name	Indicates the name of a VLANIF interface. The VLANIF interface name cannot be modified. You can select multiple interfaces each time.
DHCP Server Group Name	Indicates the name of a DHCP server group. Select a configured DHCP server from the drop-down list box. If a DHCP server based on an interface address pool is configured, all the users going online through this interface obtain IP addresses from the interface address pool.

Set parameters.
Click OK.

Delete the DHCP delay configuration.
1. Choose Service Management > DHCP > Configure DHCP Delay in the navigation tree to open the Configure DHCP Delay page.
2. Select a record and click Clear Configuration. The system asks you whether to delete the record.
3. Click OK.

Create a DHCP server group.

Choose Service Management > DHCP > Configure DHCP Delay in the navigation tree to open the Configure DHCP Delay page.

Click New to open the Create a DHCP Server Group page.

Table 2 describes the parameters on the Create a DHCP Server Group page.

**Table 2** Create a DHCP Server Group
Parameter	Description
DHCP Server Group Name	Indicates the name of a DHCP server group.
DHCP Server IP	Indicates the IP address of a DHCP server. You can configure a maximum of 20 DHCP servers in a DHCP server group. NOTE: To add a DHCP server address, click Add. To delete a DHCP server address, select it and click Delete.

Set parameters.
Click OK.

Delete a DHCP server group.
1. Choose Service Management > DHCP > Configure DHCP Delay in the navigation tree to open the Configure DHCP Delay page.
2. Select a record that you want to delete and click Delete. The system asks you whether to delete the record.
  NOTE:
  - To select a record, click the check box of the record.
  - To delete records in batches, click the check boxes of the records.
3. Click OK.