Dhcp External Server Identification Of Clients With Duplicate Mac Addresses Overview - Juniper JUNOSE SOFTWARE 11.0.X - BROADBAND ACCESS CONFIGURATION GUIDE 4-1-2010 Configuration Manual

JUNOSe 11.0.x Broadband Access Configuration Guide
ip dhcp-external recreate-subscriber-interface command from Global Configuration
mode.
When a bound DHCP client restarts the discovery process on a different primary IP
interface than the interface on which it initiated the original discovery process, the
DHCP external server application always deletes and re-creates the existing dynamic
subscriber interfaces for that client.
You must use the ip dhcp-external recreate-subscriber-interface command within
a specific virtual router context. Because you issue this command on a per-virtual
router basis, different virtual routers configured in the same router can use different
settings for this command.
In some lower-numbered JUNOSe software releases, the default behavior for the
DHCP external server was to delete and re-create the dynamic subscriber interface
after a bound client restarted the discovery process on its primary IP interface. If
you are upgrading the JUNOSe software on the router from one of these releases to
the current release, keep in mind that you must explicitly issue the ip dhcp-external
recreate-subscriber-interface command to continue to delete and re-create the
dynamic subscriber interface. The router no longer deletes and re-creates the dynamic
subscriber interface by default in this situation.
See DHCP External Server in the Known Behavior section of the JUNOSe Release Notes
for a list of the JUNOSe releases in which deleting and re-creating the dynamic
subscriber interface was the default behavior for the DHCP external server.
Related Topics
DHCP External Server Identification of Clients with Duplicate MAC Addresses
Overview
You can configure the DHCP external server application to use a combination of the
media access control (MAC) address and the gateway IP address (giaddr) to uniquely
identify DHCP clients attached to the router. Using this feature enables you to manage
DHCP clients in network environments in which MAC addresses are not unique.
In some network environments where the DHCP external server application manages
DHCP clients from multiple DHCP relays, the same MAC address might be assigned
to more than one DHCP client. This can occur, for example, when network adapters
are manufactured with the same hardware address, resulting in duplicate MAC
addresses among the DHCP clients attached to the router.
To better manage DHCP clients in network environments with multiple DHCP relays
in which MAC addresses are not unique, you can configure the DHCP external server
application to use a combination of the MAC address and the giaddr to uniquely
identify the clients connected to the router. This setting for DHCP external server is
also referred to as duplicate MAC mode.
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DHCP External Server Identification of Clients with Duplicate MAC Addresses Overview

Configuring DHCP External Server to Control Preservation of Dynamic Subscriber
Interfaces on page 526
ip dhcp-external recreate-subscriber-interface