User`s guide

XSR User’s Guide 299
Chapter 12 DHCP Services
Configuring DHCP
For example, the server may choose the least recently assigned address. As a
consistency check, the allocating server will also probe the reused address
before allocating the address - e.g., with an ICMP echo request - and the client
will also probe the newly received address - e.g., with ARP.
Assigned Network Configuration Values to Clients: Options
With the exception of IP address assignment to clients, the DHCP Server
provides a framework for passing configuration data to hosts on a TCP/IP
network. Configuration values and other control data are carried in tagged
data items which are stored in the options field of the DHCP message. The
data items themselves, also called options, are enabled on the XSR by the
options command specifying IP address, hex or ASCII string values.
Supported options are defined in the “Dynamic Host Configuration Protocol
Commands” chapter of the XSR CLI Reference Guide.
RFC-1122 specifies default values for most IP/TCP configuration parameters.
Provisioning Differentiated Network Values by Client Class
One DHCP option - supported on the XSR by the client-class command -
groups clients into classes with differentiated configuration. A DHCP Server
selects appropriate parameters for the clients belonging to this class. For
example, a Client Class can configure all enterprise users in Accounting with
a different lease time than users in Marketing.
RFC-3004 defines the User Class (Client Class) option for DHCP.
BOOTP Legacy Support
The XSR provides backward compatibility with BOOTP clients. When
configured with a manual binding, it supplies a specified IP address to the
client as well as a TFTP server IP address and file name to download (with the
next-server command).
Refer to “BOOTP Client Support Example” on page 308 for more information.