Overview - Juniper JUNOSE SOFTWARE 11.2.X - BROADBAND ACCESS CONFIGURATION GUIDE 7-20-2010 Configuration Manual

JunosE 11.2.x Broadband Access Configuration Guide
Related Topics
DHCP External Server Identification of Clients with Duplicate MAC Addresses Overview
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after the client restarts discovery, you must issue the 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.
Configuring DHCP External Server to Control Preservation of Dynamic Subscriber
Interfaces on page 519
ip dhcp-external recreate-subscriber-interface
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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