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.
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.
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.
Warning
Inadvertently selecting the Unlimited Lease Time check box could cause a network outage when the address range runs out of 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.
To configure general IPv4 DHCP properties:
Warning
Inadvertently selecting the Unlimited Lease Time check box could cause a network outage when the address range runs out of 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:
4. Save the configuration and click Restart if it appears at the top of the screen.
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
.
Note
Enabling this feature might have a significant performance impact on your appliance, depending on the number of fixed addresses you have configured.
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:
3. Save the configuration and restart DHCP service.
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