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Subscriber Interfaces and Demultiplexing Overview

You can create logical subscriber interfaces using static or dynamic demultiplexing interfaces. In addition, you can use either IP demultiplexing interfaces or VLAN demultiplexing interfaces when creating logical subscriber interfaces.

Demultiplexing (demux) interfaces are logical interfaces that share a common, underlying logical interface (in the case of IP demux) or underlying physical interface (in the case of VLAN demux). You can use these interfaces to identify specific subscribers or to separate individual circuits by IP address (IP demux) or VLAN ID (VLAN demux).

The subscriber interfaces can provide different levels of services for individual subscribers in an access network. For example, you can apply CoS parameters for each subscriber.

From Junos OS Release 18.1 onwards, packet triggered subscribers feature creates IP demultiplexing interfaces (IP demux IFL) on receiving a data packet from clients with pre-assigned IP address. The IP demultiplexing interfaces are created for both IPv4 or IPv6 data packets. On receiving the packets, the forwarding plane checks the source IP address. If the source IP address matches any one of the configured IP address or prefix ranges, the subscriber is sent to the Routing engine. The Routing Engine authenticates the subscriber with authenticating server. The authenticating server requests for volume accounting and may also request for advanced services such as firewall filter or CoS. The IP demux IFL is created with the services requested by the authenticating server. The IP demux IFL employs subscriber services in networks with statically assigned IP clients or subscribers with pre-assigned IP address.


If the source IP address does not fall within any of the IP address or prefix ranges on the interface, the IP demux IFL does not get created

Interface Sets of Static Demux Interfaces

You can group static demux interfaces to create individual subscriber interfaces using interface sets. Interface sets enable you to provide the same level of service for a group of subscribers; for example, all residential subscribers who receive the basic data service.

Figure 1 shows a subscriber interface configured using a set of IP demux interfaces with an underlying VLAN interface.

Figure 1: IP Demux Subscriber InterfaceIP Demux Subscriber Interface

Dynamic Demultiplexing Interfaces

You can configure demux interfaces to represent a dynamic subscriber interface in a dynamic profile.

Demux interfaces are dynamically created by a DHCP access method when the underlying interface for the demux interface is configured for the access method. The DHCP access model creates the demux interface with the subscriber's assigned IP address (for IP demux interfaces) or VLAN ID (for VLAN demux interfaces).

To configure an IP demux interface in the dynamic profile, you specify variables for the unit number, the name of the underlying interface, and the IP address. To configure a VLAN demux interface in the dynamic profile, you specify variables for the unit number, the name of the underlying interface, and the VLAN ID. These variables are replaced with the values that are supplied by DHCP when the subscriber logs in.

Guidelines for Configuring Demux Interfaces for Subscriber Access

When you configure static or dynamic demux interfaces for subscriber access, consider the following guidelines:

  • Only demux0 is supported. If you configure another demux interface, such as demux1, the configuration commit fails.

  • You can configure only one demux0 interface per chassis.

  • For IP demux interfaces, you can define logical demux interfaces on top of the demux0 interface (for example, demux0.1, demux0.2, and so on).

  • Hierarchical and per-unit scheduling is supported for dynamically created demux interfaces on the EQ DPC.

  • IP demux interfaces support IPv4 (family inet) and IPv6 (family inet6)).

  • IP demux subscriber interfaces over aggregated Ethernet physical interfaces are supported only for MX Series routers that have only MPCs installed. If the router has other cards in addition to MPCs, the CLI accepts the configuration but errors are reported when the subscriber interfaces are brought up.

  • You can configure IPv4 and IPv6 addressing for static and dynamic demux interfaces.

  • Demux interfaces currently support only Gigabit Ethernet, Fast Ethernet, 10-Gigabit Ethernet, and aggregated Ethernet underlying interfaces.

  • You must associate IP demux interfaces with an underlying logical interface.

  • You must associate VLAN demux interfaces with an underlying device (physical interface).

  • You cannot use a dynamic demux interface to represent multiple subscribers in a dynamic profile attached to an interface. One dynamic demux interface represents one subscriber. Do not configure the aggregate-clients option when attaching a dynamic profile to a demux interface for DHCP.


Before you make any changes to the underlying interface for a demux0 interface, you must ensure that no subscribers are currently present on that underlying interface. If any subscribers are present, you must remove them before you make changes.