Juniper JUNOSE 11.1.X - BROADBAND ACCESS CONFIGURATION GUIDE 6-4-2010, Руководство по настройке

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When you create a static subscriber interface, as described in “Configuring Static
Subscriber Interfaces” on page 615, each layer in the interface stack is created through
an existing configuration mechanism such as command-line interface (CLI) or Simple
Network Management Protocol (SNMP).
By contrast, the router creates dynamic subscriber interfaces on demand, in response
to an external event. Two types of external events can cause dynamic creation of
subscriber interfaces: when an Dynamic Host Configuration Protocol (DHCP) event
occurs or when the router detects a packet.
DHCP Servers
The DHCP event that triggers dynamic creation of subscriber interfaces occurs when
either a local DHCP server or external DHCP server assigns an IP address to a
subscriber that has issued a DHCP request. After the DHCP server assigns the IP
address and the router creates the associated dynamic subscriber interface, the
subscriber can access required network services.
DHCP Local Server and Address Allocation
You can configure the DHCP local server to operate in either equal-access mode or
standalone mode.
In standalone mode, the DHCP local server provides a basic DHCP service. The server
receives a client request for an IP address and immediately allocates the subscriber
an IP address from one of the local address pools.
In equal-access mode, the DHCP local server works with Juniper Networks Session
and Resource Control (SRC) software and the authorization, accounting, and address
assignment utility to provide an advanced subscriber configuration and management
service. After the subscriber is authenticated through RADIUS, the DHCP server
assigns the subscriber an IP address with a long lease time. This assignment of an
IP address triggers the creation of dynamic subscriber interfaces.
For more information about the DHCP servers and the SRC software, see the following
chapters:
■
“DHCP Overview Information” on page 461
■
SRC-PE Getting Started Guide , Chapter 1 , SRC Product Overview
DHCP External Server and Address Allocation
With DHCP external server, all communication between the subscriber and the DHCP
server is monitored by the E Series router. The subscriber requests an address from
the DHCP server through the E Series router. After the subscriber receives an IP
address, the subscriber can access the Internet and use the value-added services
provided by the E Series router and by the SRC software. The edge network must
be using a DHCP relay function.
The services provided by integrating the E Series router’s DHCP external server
application with SRC software are similar to those provided when the DHCP local
Dynamic Creation of Subscriber Interfaces
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Chapter 25: Configuring Subscriber Interfaces