Specifications
86 Chapter 4. Configuring Special Features
Warning: The client will not be aware that the administrator has changed or released a client lease!
To change the client lease expiration time to a given value:
dhcp set expire <ipaddr> <hours>
Setting the expiration time to ÒdefaultÓ will cause the server to compute the lease time using the algorithm as
described in Setting the Lease Time, page 85.
To release the client lease so it becomes available for other assignments:
dhcp clear expire <ipaddr>
Setting Option Values
Administrators can set values for global options, for options specific to a subnetwork, or for options specific to a
client lease.
Note: See RFC 2131/2132 for the description of various options.
Concepts
The server returns values for options explicitly requested in the client request. It selects the values to return
based on the following algorithm:
1. If the value is defined for the client, then the server returns the requested value for an option.
2. If the value for the option has not been set for the client, then the server returns the value option if it has
been defined for the subnetwork.
3. If the value option does not exist for the client and does not exist for the subnetwork, then the server
returns the value option if it has been defined globally.
4. If the value option is not defined anywhere, the server does not return any value for that option in its
reply to the client request.
Important: When the server replies to a client:
¥ It does not return any option values not requested by the client.
¥ It does not support the definition of a ÒclassÓ of clients.
¥ It does not return any non-default option values unless the client requests the option value and the server
has a value defined for that option.
¥ It does not return any non-default values on the clients subnet unless the client requests the value for that
option.
Commands for Global Option Values
To set the value for a global option, use:
dhcp set valueoption <code> <value>...
The code can be a number between 1 and 61 or a keyword.
To see the list of predefined and user-defined options, use:
dhcp list definedoptions