Defining Lease Times

A DHCP lease time specifies the amount of time that the DHCP server grants to a network device the permission to use a particular IP address. 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.

You can set parameters to control how the DHCP server responds to lease requests for clients and hardware. When you choose to deny the lease requests, the application does not assign IP addresses to the clients and hardware that are defined in the list. You can also configure the DHCP server to assign or deny IP addresses to unknown DHCP clients. Unknown clients include clients that are not roaming NIOS-X Servers and clients that do not have fixed addresses or DHCP NIOS-X Server entries.

NIOS-X Servers are authoritative for their lease data. The Universal DDI appliance periodically saves the changes to the leases in the cloud. The application does not support lease history and only current leases are available.

To control how the application assigns leases to client requests:

1. In the Infoblox Portal, click Manage > IPAM/DHCP > Global DHCP Configuration.

2. On the Global DHCP Configuration page, click Leases and configure the following settings for IPv4 or IPv6 leases:
   

   • Lease Time: Enter the lease time and select the time unit from the drop-down list. The maximum lease time allowed is 5 years. Universal DDI will now automatically convert imported unlimited DHCP lease times to the maximum supported by the systems, which is 5 years.

   • Renewal Time and Rebinding Time: When a DHCP lease expires, the DHCP client attempts to renew the lease by contacting the original leasing DHCP server by requesting a new lease. The time when the DHCP client requests the renewal of the lease is called Renewal Time. If the original leasing server does not respond by a certain time, the DHCP client broadcasts a request to other servers for lease renewal. The point at which the DHCP client broadcasts the a request for lease renewal from other servers, is called the Rebinding Time. The Renewal Time and Rebinding Time options are only available at the subnet level and not available at the global level. 

     • Renewal Time (T1): Enter the renewal time and select the time unit from the drop-down list.
     • Rebinding Time (T2): Enter the renewal time and select the time unit from the drop-down list.

   • Allow Leases for Unknown Clients: Select this check box to assign IP addresses to unknown DHCP clients. Unknown DHCP clients include clients that are not roaming NIOS-X Servers and clients that do not have fixed addresses or DHCP NIOS-X Server entries. Clear the check box to deny IP addresses to unknown DHCP clients.

   • Ignore UID when issuing IPv4 DHCP Leases: Select this check box to set the DHCP server to ignore the UID (unique client identifier) of a DHCP client during lease lookups and allocations for a particular subnet. If this setting is enabled, when a DHCP client places a request for a new lease, the DHCP server identifies the DHCP client solely based on the MAC address. This is not applicable for IPv6 leases.
     

   • IGNORE LEASE REQUESTS FROM: Click Add to add DHCP clients or hardware whose lease request must be denied. To delete an entry, select the respective check box and click Remove.

3. Click Save & Close to save the details or click Cancel to exit.