Juniper JUNOSE 11.0.X MULTICAST ROUTING, Руководство по настройке

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If the SRC software is configured, the router also performs the following actions:
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Alerts the SRC software that the dynamic subscriber interface exists
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Alerts the SRC software that the subscriber’s address exists and provides DHCP
options
The SRC software then provides its enhanced services to the subscriber.
The E Series router monitors all traffic between the subscriber and the DHCP server,
and resets the shadow lease by monitoring the DHCP server/client lease renewal.
When the subscriber disconnects, the shadow lease will eventually expire. The E
Series router then performs the following actions:
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Deletes the subscriber’s dynamic subscriber interface
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Alerts the SRC software that the dynamic subscriber interface has been deleted
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Alerts the SRC software that the subscriber’s address has been deleted
For additional information on managing client bindings, see “Viewing and Deleting
DHCP Client Bindings” on page 460.
Preservation of Dynamic Subscriber Interfaces with DHCP External Server Overview
You can configure the DHCP external server application to control whether the router
preserves or deletes and re-creates a DHCP client’s existing dynamic subscriber
interface in certain situations.
The DHCP discovery process assigns an IP address to a DHCP client. A client initiates
the discovery process on a primary IP interface in the router. When this process
completes successfully, the IP subscriber manager application may create a dynamic
subscriber interface for the client that exists with the client's primary interface. A
client normally receives broadcast traffic, such as the traffic associated with the DHCP
discovery process, on its primary interface. A client normally receives unicast traffic,
such as the traffic associated with the DHCP renewal process, on its dynamic
subscriber interface if one exists.
A DHCP client that has successfully completed the discovery process and has been
assigned an IP address in the DHCP external server application is referred to as a
bound client . An IP address is leased to a client for a specified period of time. Before
the lease period expires, most bound DHCP clients typically use the DHCP renewal
process to extend their IP address lease. However, some bound DHCP clients might
extend their IP address lease by restarting the DHCP discovery process instead of
using the DHCP renewal process.
When a bound DHCP client on a dynamic subscriber interface extends its address
lease by restarting the discovery process on its primary IP interface, you can configure
the DHCP external server application to control whether the client’s existing dynamic
subscriber interface is preserved, or deleted and re-created. By default, the DHCP
external server preserves the client’s existing dynamic subscriber interface in this
situation. To configure the DHCP external server to delete and re-create the client’s
dynamic subscriber interface after the client restarts discovery, you must issue the
Preservation of Dynamic Subscriber Interfaces with DHCP External Server Overview
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Chapter 21: Configuring the DHCP External Server Application