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Enabling VLAN Tagging

You can configure the router to receive and forward single-tag frames, dual-tag frames, or a mixture of single-tag and dual-tag frames.

  1. To configure the router to receive and forward single-tag frames with 802.1Q VLAN tags, include the vlan-tagging statement at the [edit interfaces interface-name] hierarchy level:
  2. To configure the router to receive and forward dual-tag frames with 802.1Q VLAN tags, include the stacked-vlan-tagging statement at the [edit interfaces interface-name] hierarchy level:
  3. Mixed tagging is supported for all router Gigabit and 10-Gigabit Ethernet interfaces on MX Series routers and for aggregated Ethernet interfaces with member links in IQ2 and IQ2-E PICs or in MX Series DPCs. Mixed tagging enables to configure two logical interfaces on the same Ethernet port, one with single-tag framing and one with dual-tag framing.
    [upoovaiahpk/appu 04/12/25] Removed reference to fast ethernet per Junos Detox Phase 2.

    To configure mixed tagging:

    1. Configure the flexible-vlan-tagging statement at the [edit interfaces ge-fpc/pic/port] hierarchy level.
    2. Configure the vlan-tags statement with inner and outer options or the vlan-id statement at the [edit interfaces ge-fpc/pic/port unit logical-unit-number] hierarchy level:
    Note:

    If you configure the physical interface MTU for mixed tagging, then you must increase the MTU to 4 bytes more than the MTU value you would configure for a standard VLAN-tagged interface.

    For example, if the MTU value is configured to be 1018 on a VLAN-tagged interface, then the MTU value on a flexible VLAN tagged interface must be 1022—4 bytes more. The additional 4 bytes accommodates the future addition of a stacked VLAN tag configuration on the same physical interface.

    If the same physical interface MTU value is configured on both the VLAN and flexible VLAN-tag routers, the L2 circuit configuration does not come up and a MTU mismatch is logged. However, normal traffic flow is unaffected.

    For encapsulation type flexible-ethernet-services, all VLAN IDs are valid.

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