Ethernet Interfaces And Vlans; Figure 18: Subscriber Interfaces Over Ethernet - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BROADBAND ACCESS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

JunosE 11.3.x Broadband Access Configuration Guide

Ethernet Interfaces and VLANs

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interface directly on an Ethernet interface, the subscriber interface does not operate until
you assign an IP address to the Ethernet interface.
To configure a subscriber interface you must associate either a source address or a
destination address with the interface. The router receives packets on a subscriber
interface after demultiplexing the packet according to the specified source address or
destination address. You can associate multiple source addresses or multiple destination
addresses with a subscriber interface. However, a single primary interface and its
associated subscriber interfaces can only demultiplex source addresses or destination
addresses at any given time.
For example, Figure 18 on page 598 illustrates the relationship between subscriber
interfaces, an associated primary IP interface, and an associated Ethernet interface.

Figure 18: Subscriber Interfaces over Ethernet

When the router receives traffic on a primary interface, the primary interface performs a
lookup in its demultiplexing table. If the result of the lookup is a subscriber interface, the
traffic is received on the associated subscriber interface.
NOTE: You can use the set dhcp relay giaddr-selects-interface command
to specify that the primary interface is identified by information in the giaddr
field of DHCP ACK messages. By default, the router identifies the primary
interface based on the interface used by the DHCP-destined packets. See
"Using the Giaddr to Identify the Primary Interface for Dynamic Subscriber
Interfaces" on page 498 .
In the absence of VLANs, Ethernet does not have a demultiplexing layer. A subscriber
interface adds a demultiplexing layer for an Ethernet interface that is configured without
VLANs. Using subscriber interfaces, the router can demultiplex or separate the traffic
associated with different subscribers.
You can configure subscriber interfaces with VLANs. If you do so, the E Series router
demultiplexes packets by using first the VLAN and then the subscriber interface.
Copyright © 2010, Juniper Networks, Inc.