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Demultiplex Interfaces

Learn about demultiplex (demux) interfaces and how to configure IP demultiplex interfaces and VLAN demultiplex interfaces.

Demultiplex (demux) interfaces are logical interfaces that share a common underlying interface. Demux interfaces allows you to create multiple logical subscriber interfaces from a single physical or logical connection.

Demux interfaces enable you to identify and separate individual subscribers in two primary ways: IP demultiplex interfaces and demultiplex interfaces.

Demux interfaces support only Gigabit Ethernet, Fast Ethernet, 10-Gigabit Ethernet, or aggregated Ethernet underlying interfaces. Use Feature Explorer to confirm platform and release support for demultiplex (demux) interfaces.

You can create logical subscriber interfaces using dynamic or static demultiplex interfaces. To configure dynamic VLAN demux interfaces, see Configuring Dynamic Subscriber Interfaces Using VLAN Demux Interfaces in Dynamic Profiles.

Table 1: Static Demultiplex Interfaces and Configuration
Static Demultiplex Interfaces Know More

IP Demultiplex Interface

  • IP demux interfaces use the IP source address or IP destination address to demultiplex received packets when the subscriber is not uniquely identified by a Layer 2 circuit.

  • To determine which IP demux interface to use, the destination or source prefix is matched against the destination or source address of packets that the underlying interface receives. The underlying interface family type must match the demux interface prefix type.

  • To configure IP demultiplex interface, see Configure an IP Demultiplex Interface.

VLAN Demultiplex Interface

  • VLAN demux interfaces use the VLAN ID to demultiplex received packets when the subscriber is not uniquely identified. A VLAN demux interface uses an underlying logical interface to receive packets.

  • To determine which VLAN demux interface to use, the VLAN ID is matched against that which the underlying interface receives.

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

  • To configure VLAN demultiplex interface, see Configure a VLAN Demultiplex Interface.

Guidelines to Configure a Demultiplex Interface

Keep the following guidelines in mind when you configure the demux interface:

  • Demux interfaces are supported on MX Series routers only.

  • 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, but you can define logical demux interfaces on top of it (for example, demux0.1, demux0.2, and so on).

  • If the address in a received packet does not match any demux prefix, the packet is logically received on the underlying interface. For this reason, the underlying interface is often referred to as the primary interface.

Guidelines to Configure an IP Demultiplex Interface

Remember the following guidelines when you configure an IP demultiplex interface:

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

  • The demux underlying interface must reside on the same logical system as the demux interfaces that you configure over it.

  • IP demux interfaces currently supports the Internet Protocol version 4 (IPv4) suite inet and Internet Protocol version 6 (IPv6) suite inet6 family types.

  • You can configure more than one demux prefix for a given demux unit. However, you cannot configure the exact same demux prefix on two different demux units with the same underlying interface.

  • You can configure overlapping demux prefixes on two different demux units with the same underlying prefix. However, under this configuration, best match rules apply (in other words, the most specific prefix wins).

Guidelines to Configure a VLAN Demultiplex Interface

Remember the following guidelines when you configure a VLAN demultiplex interface:

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

  • The demux underlying interface must reside on the same logical system as the demux interfaces that you configure over it.

  • VLAN demux interfaces currently supports the Internet Protocol version 4 (IPv4) suite inet and Internet Protocol version 6 (IPv6) suite inet6 family types.

Configure an IP Demultiplex Interface

To configure an IP demultiplex interface, you must configure the demux prefixes that are used by the underlying interface and then configure the IP demultiplexing interface as explained in the following tasks:

Configure an IP Demux Underlying Interface

To configure a logical interface as an IP demux underlying interface with demux source:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:
  2. Configure the interface as fe-x/y/z and the logical interface with the unit statement. In this procedure, we show a Fast Ethernet interface as an example.
  3. Configure the logical demux source family type on the IP demux underlying interface as inet or inet6, or both.

    or

  4. (Optional) To improve datapath performance for DHCPv4 subscribers, specify that only subscribers with 32-bit prefixes are allowed to come up on the interface.

    This step requires that you specify the demux-source as only inet. A commit error occurs if you specify only inet6 or both inet and inet6.

  5. Save the configuration and move to top of the hierarchy level.

To configure a logical interface as an IP demux underlying interface with demux destination:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:

  2. Configure the interface as fe-x/y/z and the logical interface with the unit statement.

  3. Configure the logical demux destination family type on the IP demux underlying interface as inet or inet6.

    See demux-destination (Underlying Interface).

  4. Save the configuration and move to top of the hierarchy level.

Configure the IP Demux Interface

You can configure one or more logical demux source prefixes or destination prefixes after specifying an underlying interface for the static demux interface to use. This underlying interface must reside on the same logical system as the demux interface.

You configure demux prefixes for use by the underlying interface. The demux prefixes can represent individual hosts or networks. For a given demux interface unit, you can configure either demux source or demux destination prefixes but not both.

You can choose not to configure a demux source or demux destination prefix. This type of configuration results in a transmit-only interface.

To configure the IP demux interface with source prefix:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:
  2. Configure the interface as a logical demux interface (for example, demux0 interface) and configure the logical interface with the unit statement.

    You can configure only one demux0 interface per chassis, but you can define logical demux interfaces on top of it (for example, demux0.1, demux0.2, and so on).

    See demux0 (Static Interface).
  3. Configure the underlying interface on which the demux interface is running under the demux-options statement.
    See demux-options (Static Interface).
  4. Configure the protocol family.
  5. Configure one or more logical demux source prefixes (IP address). The prefixes are matched against the source address of packets that the underlying interface receives. When a match occurs, the packet is processed as if it was received on the demux interface.
    See demux-source (Demux Interface).
  6. Save the configuration and move to top of the hierarchy level.

To configure the IP demux interface with destination prefix:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:

  2. Configure the interface as a logical demux interface (for example, demux0 interface) and configure the logical interface with the unit statement.

    You can configure only one demux0 interface per chassis, but you can define logical demux interfaces on top of it (for example, demux0.1, demux0.2, and so on).

  3. Configure the underlying interface on which the demux interface is running under the demux-options statement.

  4. Configure the protocol family.

  5. Configure one or more logical demux destination prefixes. The prefixes are matched against the destination address of packets that the underlying interface receives. When a match occurs, the packet is processed as if it was received on the demux interface.

    See demux-destination (Demux Interface).

  6. Save the configuration and move to top of the hierarchy level.

Configure a VLAN Demultiplex Interface

To configure a VLAN demux interface, you must configure the demux prefixes that are used by the underlying interface and then configure the VLAN demultiplexing interface as explained by the following tasks:

Configure a VLAN Demux Underlying Interface

To configure a logical interface as a VLAN demux underlying interface with demux source:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:
  2. Configure the interface as fe-x/y/z and the logical interface with the unit option.
  3. Configure the VLAN ID. The VLAN ID is used to determine which VLAN demux interface to use, that is the VLAN ID is matched against that which the underlying interface receives.
    See vlan-id.
  4. Configure the logical demux source family type on the VLAN demux underlying interface as inet or inet6.
    See demux-source (Underlying Interface).
  5. Save the configuration and move to top of the hierarchy level.

To configure a logical interface as a VLAN demux underlying interface with demux destination:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:

  2. Configure the interface as fe-x/y/z and the logical interface with the unit option.

  3. Configure the VLAN ID. The VLAN ID is used to determine which VLAN demux interface to use, that is the VLAN ID is matched against that which the underlying interface receives.

  4. Configure the logical demux destination family type on the VLAN demux underlying interface as inet or inet6.

    See demux-destination (Underlying Interface).

  5. Save the configuration and move to top of the hierarchy level.

Configure the VLAN Demux Interface

You can configure one or more logical demux source prefixes or destination prefixes after specifying an underlying interface for the static demux interface to use. This underlying interface must reside on the same logical system as the demux interface.

You configure demux prefixes for use by the underlying interface. The demux prefixes can represent individual hosts or networks. For a given demux interface unit, you can configure either demux source prefix or demux destination prefixes but not both.

You can choose not to configure a demux source prefix or a demux destination prefix. This type of configuration results in a transmit-only interface

To configure VLAN demux interface with demux source prefix:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:
  2. Configure the interface as a logical demux interface (for example, demux0 interface) and configure the logical interface with the unit statement.

    You can configure only one demux0 interface per chassis, but you can define logical demux interfaces on top of it (for example, demux0.1, demux0.2, and so on).

    See demux0 (Static Interface).
  3. Configure the underlying interface on which the demux interface is running under the demux-options statement.
    See demux-options (Static Interface).
  4. Configure the protocol family for the interface.
  5. Configure one or more logical demux source prefixes. The prefixes are matched against the source address of packets that the underlying interface receives. When a match occurs, the packet is processed as if it was received on the demux interface.
    See demux-source (Demux Interface).
  6. Save the configuration and move to top of the hierarchy level.

To configure VLAN demux interface with demux destination prefix:

  1. In configuration mode, go to the [edit interfaces] hierarchy level:

  2. Configure the interface as a logical demux interface (for example, demux0 interface) and configure the logical interface with the unit statement.

    You can configure only one demux0 interface per chassis, but you can define logical demux interfaces on top of it (for example, demux0.1, demux0.2, and so on).

  3. Configure the underlying interface on which the demux interface is running under the demux-options statement.

  4. Configure the protocol family for the interface.

  5. Configure one or more logical demux destination prefixes. The prefixes are matched against the destination address of packets that the underlying interface receives. When a match occurs, the packet is processed as if it was received on the demux interface.

    See demux-destination (Demux Interface).

  6. Save the configuration and move to top of the hierarchy level.

Verify a Demux Interface Configuration

Purpose

Check the configuration of a demux interface and its underlying interface when the following are configured:

  • Two VLANs are configured, where each VLAN consists of two IP demux interfaces.

  • One VLAN demultiplexes based on the source address

  • The other VLAN demultiplexes based on the destination address.

Action

From configuration mode on the router, run the show interfaces fe-0/0/0 and show interfaces demux0 configuration mode commands.

MAC Address Validation on Static Demultiplex Interfaces

MAC address validation enables the router to validate that received packets contain a trusted IP source and an Ethernet MAC source address.

MAC address validation is supported on static demux interfaces on MX routers only.

There are two types of MAC address validation that you can configure:

  • Loose

    • Forwards packets when both the IP source address and the MAC source address match one of the trusted address tuples.

    • Drops packets when the IP source address matches one of the trusted tuples, but the MAC address does not support the MAC address of the tuple

    • Continues to forward packets when the source address of the incoming packet does not match any of the trusted IP addresses.

  • Strict

    • Forwards packets when both the IP source address and the MAC source address match one of the trusted address tuples.

    • Drops packets when the MAC address does not match the tuple's MAC source address, or when IP source address of the incoming packet does not match any of the trusted IP addresses.

Configure MAC Address Validation on Static IP Demultiplex Interfaces

MAC address validation enables the router to validate that received packets contain a trusted IP source and an Ethernet MAC source address.

To configure MAC address validation for an IP demux interface:

  1. In configuration mode, go to the [edit interfaces demux0 unit logical-unit-number] hierarchy level:
  2. Configure the protocol family for the interface.
  3. Configure the mac-validate statement to validate source MAC address with loose or strict options.
  4. Save the configuration and move to top of the hierarchy level.

Configure MAC Address Validation on Static VLAN Demux Interfaces

MAC address validation enables the router to validate that received packets contain a trusted IP source and an Ethernet MAC source address.

To configure MAC address validation for a VLAN demux interface:

  1. In configuration mode, go to the [edit interfaces demux0 unit logical-unit-number] hierarchy level:
  2. Configure the protocol family for the interface.
  3. Configure the mac-validate statement to validate source MAC address with loose or strict options.
  4. Save the configuration and move to top of the hierarchy level.

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