server creates an entry in its internal client table to keep track of the client state, then
sends a DHCP offer packet to the client.
3. On receipt of the offer packet, the DHCP client selects the DHCP local server from
which to obtain configuration information and sends a request packet indicating the
DHCP local server selected to grant the address and configuration information.
4. The selected DHCP local server sends an acknowledgment packet to the client that
contains the client address lease and configuration parameters. The server also installs
the host route and Address Resolution Protocol (ARP) entry, and then monitors the
lease state.
Minimal Configuration for Clients
The extended DHCP local server provides a minimal configuration to the DHCP client if
the client does not have DHCP option 55 configured. The server provides the subnet mask
of the address-assignment pool that is selected for the client. In addition to the subnet
mask, the server provides the following values to the client if the information is configured
in the selected address-assignment pool:
•
router—A router located on the client’s subnet. This statement is the equivalent of
DHCP option 3.
•
domain name—The name of the domain in which the client searches for a DHCP server
host. This is the default domain name that is appended to hostnames that are not fully
qualified. This is equivalent to DHCP option 15.
•
domain name server—A Domain Name System (DNS) name server that is available to
the client to resolve hostname-to-client mappings. This is equivalent to DHCP option
6.
DHCP Local Server and Address-Assignment Pools
In the traditional DHCP server operation, the client address pool and client configuration
information reside on the DHCP server. With the extended DHCP local server, the client
address and configuration information reside in centralized address-assignment pools,
which are managed independently of the DHCP local server and which can be shared by
different client applications.
The extended DHCP local server also supports advanced pool matching and the use of
named address ranges. You can also configure the local server to use DHCP option 82
information in the client PDU to determine which named address range to use for a
particular client. The client configuration information, which is configured in the
address-assignment pool, includes user-defined options, such as boot server, grace
period, and lease time.
Configuring the DHCP environment that includes the extended DHCP local server requires
two independent configuration operations, which you can complete in any order. In one
operation, you configure the extended DHCP local server on the router and specify how
the extended DHCP local server determines which address-assignment pool to use. In
Copyright © 2017, Juniper Networks, Inc.316
ACX Series Universal Access Router Configuration Guide
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