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    Dynamic VLAN Subinterfaces over Static VLAN Major Interfaces Overview

    E Series routers support configuration of dynamic VLAN subinterfaces over static VLAN major interfaces over Ethernet.

    When you configure the dynamic VLAN subinterface, you can enable autodetection and dynamic creation of the following upper-layer encapsulation types:

    • IP
    • PPPoE

      Note: Unlike ATM, which supports dynamic upper interfaces over static ATM 1483 subinterfaces, you must configure a dynamic VLAN subinterface to enable autodetection and dynamic creation of IP and PPPoE interfaces.

    Figure 1 shows the dynamic upper-interface columns supported by dynamic VLAN subinterfaces, and indicates which layers in the columns are static and dynamic.

    Figure 1: Dynamic Interface Columns over Dynamic VLAN Subinterfaces

    Dynamic Interface Columns over Dynamic
VLAN Subinterfaces

     

    Unlike ATM 1483, you can configure both IP and PPPoE over a single dynamic VLAN subinterface (Figure 2).

    Figure 2: Dynamic IP and PPPoE over Single Dynamic VLAN Subinterface

    Dynamic IP and PPPoE over Single Dynamic
VLAN Subinterface

    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 provide you with the flexibility of having the dynamic interface column created automatically only when the subscriber logs in.

    Figure 3 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.

    Figure 3: Dynamic VLAN Subinterfaces for Subscribers

    Dynamic VLAN Subinterfaces for Subscribers

    For example, if an S-VLAN is assigned at the DSLAM, and each DSLAM subscriber at the DSLAM is assigned a unique VLAN ID, the JunosE Software dynamically constructs a VLAN-based interface column using that S-VLAN/VLAN ID pair when the subscriber logs in.

    For more information about the attributes of VLAN and S-VLAN subinterfaces, see VLAN Overview and S-VLAN Overview.

    Published: 2014-08-14