When you configure general IPv4 DHCP properties at the Grid level, the configuration applies to the entire Grid. Though you can set DHCP properties at the Grid level, you can enable DHCP services at the member level only. Infoblox recommends that you configure the DHCP properties before you enable DHCP on the appliance. Depending on the properties, you can override some of them for the members, networks, DHCP ranges, fixed addresses, reservations, host addresses, and roaming hosts. To override an inherited DHCP property, click Override next to the property to enable the configuration.

Specifying Authoritative

Only authoritative DHCP servers can send clients DHCPNAK messages when they request invalid IP addresses. For example, a client moves to a new subnet and broadcasts a DHCPREQUEST message for its old IP address. An authoritative DHCP server responds with a DHCPNAK, causing the client to move to the INIT state and to send a DHCPDISCOVER message for a new IP address. Authoritative servers also respond to DHCPINFORM messages from clients that receive their IP addresses from the DHCP server and require additional options after the initial leases have been granted.

Defining Lease Times

When you configure DHCP general properties, you can specify the length of time the DHCP server leases an IP address to a client. The default on the appliance is 12 hours, and you can change this default according to your network requirements. There are a number of factors to consider when setting the lease time for IP addresses, such as the types of resources and clients on the network, and impact to traffic and performance. With NIOS appliances, you can set lease times at different levels, based on these factors. You can also select the Unlimited Lease Time check box to grant unlimited lease time to IP addresses.

You can set a default lease time at the Grid level and then override this setting for specific members, network containers, networks, IP address ranges or fixed addresses when appropriate.

Configuring General IPv4 Properties

To configure general IPv4 DHCP properties:

1. Grid: From the Data Management tab, select the DHCP tab, and then click Grid DHCP Properties from the Toolbar.
   Member: From the Data Management tab, select the DHCP tab -> Members tab -> Members -> member check box, and then click the Edit icon.
   Network: From the Data Management tab, select the DHCP tab -> Networks tab -> Networks -> network check box, and then click the Edit icon.
   Network Container: From the Data Management tab, select the IPAM tab -> network_container check box, and then click the Edit icon.
   DHCP Range: From the Data Management tab, select the DHCP tab  > Networks tab -> Networks -> network->addr_range check box, and then click the Edit icon.
   Fixed Address: From the Data Management tab, select the DHCP tab -> Networks tab -> Networks -> network-> fixed_address check box, and then click the Edit icon.
   Reservation: From the Data Management tab, select the DHCP tab > Networks tab -> Networks -> network->reservation check box, and then click the Edit icon.
2. In the DHCP Properties editor of a Grid or member, select the General Basic tab. For all other objects, click Toggle Advanced Mode if the editor is in basic mode. When the additional tabs appear, select the IPv4 DHCP Options Advanced tab.
3. Complete the following:

• • Authoritative: Select DHCP server is authoritative to set the DHCP server as authoritative for the domain. This can be set for the Grid, member, network container, network and range.
  • Lease Time: Enter the lease time and select the time unit from the drop-down list. The default is 12 hours.
    • Unlimited Lease Time: Select this option to set an infinite lease time for all IP addresses.

To set all other properties for a Grid or member, toggle to the advanced mode and select the General Advanced tab to complete the following:

• • Ignore Optionlist: Select Ignore optionlist requested by client and return all defined options if you want the appliance to ignore the requested list of options in the DHCPREQUEST messages it receives from DHCP clients, and to include all the configured options in the DHCPACK and DHCPOFFER messages it sends back to the clients.
  • LEASEQUERY: Select Allow LEASEQUERY to enable the DHCP server to respond to DHCPLEASEQUERY messages.

    4. Save the configuration and click Restart if it appears at the top of the screen.

Configuring Fixed Addresses without Restarting DHCP Service

When you configure or modify a fixed address, a DHCP service restart is required by default in order for the new configuration to take effect. You can override this default behavior by enabling the appliance to take immediate action when you configure or modify a fixed address outside a DHCP range without restarting DHCP service. You can enable this feature at the Grid or member level. Note that when you enable this feature, you cannot use the CLI command set dhcp_expert_mode.

For Cloud Network Automation deployment, this feature is automatically enabled on the Cloud Platform Appliance that has a valid Cloud Platform license installed. For information about Cloud Network Automation, see Deploying Cloud Network Automation.
To enable immediate fixed address configuration:

1. Grid: From the Data Management tab, select the DHCP tab, and then click Grid DHCP Properties from the Toolbar.
   Member: From the Data Management tab, select the DHCP tab -> Members tab -> member check box, and then click the Edit icon.
2. In the DHCP Properties editor, click Toggle Advanced Mode if the editor is in basic mode. When the additional tabs appear, click the General tab -> Advanced tab and complete the following:

• • Immediate FA Configuration: Select this check box to enable the new configuration immediately without restarting DHCP service when you modify or delete a fixed address.

     3. Save the configuration and restart DHCP service.