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Configuring an MPLS-Based VLAN CCC with Pop, Push, and Swap and Control Passthrough

For providing Layer 2 VPN services across your network, you might want to configure the ability to push, pop or swap 802.1Q tags on frames entering and leaving edge routers, allowing you to use a single VLAN-circuit cross-connect (CCC) [VLAN-CCC] logical interface to handle both dual-tag and single-tag packets. This feature thus provides interoperability between Layer 2 services with a distinct VLAN at the local or remote end or in instances where a Layer 2 service comes with a certain VLAN, but the remote peer has a different VLAN or no VLAN.

This feature includes the ability to enable passthrough of certain Ethertype/DMAC-matched frames over the Layer 2 circuit after successful VLAN tag operations on the VLAN CCC logical interface.

If you configure this feature, VLAN tags are applied when traffic is sent to and from the Layer 2 circuit interface. The pop, push, and swap operations are performed only on the outer tag. The pop VLAN tag removes the VLAN tag from the top of the VLAN tag stack. The push VLAN tag adds a new outer VLAN tag, and the swap VLAN tag replaces the existing outer VLAN tag with the new VLAN tag.

You can configure inet, inet6, or VLAN-CCC connections on a single Ethernet network interface or an aggregated Ethernet interface, enabling you to set different forwarding rules for tagged and untagged traffic on the same interface. For example, you can forward tagged packets over the Layer 2 circuit and route untagged traffic in native VLAN mode.


Limitations for this feature on PTX routers are:

  • VLAN operations on STP and CDP packets are not supported.

  • You can’t configure the VLAN-CCC logical interface with the native VLAN ID.

  • LACP point-to-point connections between PE routers do not work if you configure l2circuit-control-passthrough. (Static LAG works, however.)

To configure a PE router with a VLAN CCC, an MPLS-based Layer 2 circuit, VLAN pop, push, and swap operations, and enabling passthrough of certain Ethertype/DMAC-matched frames:


The following procedure uses actual interface names for the router’s network interfaces instead of the variable interface-name so that you can quickly see their configuration differences. Remember that you can also configure the feature on aggregated Ethernet interfaces.

  1. Configure OSPF on the loopback (or router address) and core interface:

    The routing protocol can be OSPF or IS-IS.

  2. Enable traffic engineering for the routing protocol:
  3. Configure an IP address for the loopback interface and for the core interface:
  4. Configure the customer edge interface as a Layer 2 circuit from the local PE router to the other PE router:

    Use the router address of the other router as the neighbor address. It is the virtual circuit identifier together with the neighbor address that provides the unique address for the circuit.

  5. Configure MPLS on the core interfaces:
  6. Configure LDP on the loopback interface and the core interfaces:
  7. Configure family mpls on the logical unit of the core interface:

    You can enable family mpls on either individual interfaces, aggregated Ethernet interfaces, or tagged VLAN interfaces.

  8. Specify the router ID:
  9. Enable VLAN tagging on the customer edge interface of the local PE router:
  10. Configure the customer edge interface to use flexible Ethernet services encapsulation:
  11. Configure the logical unit of the customer edge interface with a VLAN ID:
  12. Configure the logical unit on the customer edge interface to use VLAN CCC encapsulation:
  13. Configure the logical unit on the customer edge interface to pop the tag off the input VLAN and then push the tag to the output VLAN:
  14. (Optional) Configure Layer 2 circuit traceoptions:
  15. (Optional) Configure the VLAN CCC logical interface so that encapsulation mismatches and MTU mismatches between this interface and the interface on the other PE router are ignored:
  16. To enable passthrough of certain Ethertype/DMAC-matched frames, configure Layer 2 circuit control passthrough: