Juniper JUNOSE 11.1.X - LINK LAYER CONFIGURATION 4-7-2010, Configuration Manual

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About Configuring Dynamic VLAN Subinterfaces
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:
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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
provide you with the flexibility of having the dynamic interface column created
automatically only when the subscriber logs in.
Figure 59 on page 661 displays the relationship between the central office, digital
subscriber line access multiplexers (DSLAMs), and subscribers. The subscribers are
connected to the DSLAMS through Gigabit Ethernet interfaces.
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Configuring VLAN Dynamic Subinterfaces
JUNOSe 11.1.x Link Layer Configuration Guide