About Configuring Dynamic Vlan Subinterfaces; Overview And Benefits - Juniper JUNOSE SOFTWARE 11.2.X - LINK LAYER CONFIGURATION GUIDE 7-7-2010 Configuration Manual

JunosE 11.2.x Link Layer Configuration Guide

About Configuring Dynamic VLAN Subinterfaces

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Figure 60: Dynamic IP and PPPoE over Single Dynamic VLAN Subinterface
This section introduces important concepts that you need to understand before you
configure dynamic VLAN subinterfaces.

Overview and Benefits

When you configure dynamic VLAN subinterfaces over static VLAN major interfaces, you
must configure the VLAN major interface, including the attributes of the VLAN major
interface. VLAN major interface attributes include profile assignments and
autoconfiguration settings.
As part of the configuration process, you create a VLAN base profile, which can optionally
include nested profile assignments, to define the attributes required to configure the
dynamic VLAN subinterface and the dynamic upper-layer encapsulation types built over
it.
When the router receives a packet, it examines the packet for a VLAN ID or double-tagged
S-VLAN ID. You can also configure the router to further examine the packet for
agent-circuit-identifier information. Based on these values and the configuration data
received from a profile, the router creates all dynamic layers above the VLAN layer, starting
with the lowest dynamic layer. For example, in the case of a dynamic PPPoE interface,
the router creates the interfaces in the following order:
Dynamic VLAN subinterface
PPPoE interface
PPP interface
IP interface
If any layer of the dynamic portion of the interface column fails to be created, then the
interface creation fails and the connection is denied. All dynamic layers above the VLAN
subinterface are destroyed, starting with the highest dynamic layer. VLAN subinterfaces
are persistent; after they are created, they cannot be destroyed, unless the operational
state changes to down.
Dynamic VLAN subinterfaces function identically to static VLAN subinterfaces, except
for the manner in which they are created and configured. However, dynamic VLANs
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