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FAT Flow Labels in EVPN-VPWS Routing Instances

FAT Flow Labels Overview introduces how LDP-signaled pseudowires in an MPLS network can use flow-aware transport (FAT) flow labels (defined in RFC 6391, Flow-Aware Transport of Pseudowires over an MPLS Packet Switched Network) to load-balance traffic in virtual private LAN service (VPLS) and virtual private wire service (VPWS) networks.

Starting in Junos OS Release 21.1R1, you can enable provider edge devices in an EVPN-MPLS network to use flow-aware transport (FAT) flow labels to load-balance traffic across pseudowires in an EVPN-VPWS routing instance. In this environment, the local and remote devices establish an EVPN connection between the local and remote provider edge (PE) devices using BGP signaling, and can use LDP or RSVP tunnels to create the pseudowire.

How to Enable FAT Pseudowire Flow Labels in an EVPN-VPWS Instance

You can enable FAT flow labels in a routing instance of type evpn-vpws for pseudowires associated with the routing instance.

This environment supports enabling FAT flow label push and pop operations on pseudowire traffic only with a static configuration. The devices don't actively use the signaling mechanism described in RFC 6391 to ensure both ends communicate that they can handle flow labels. As a result, you must use flow-label-transmit-static and flow-label-receive-static (instead of flow-label-transmit and flow-label-receive) on all of the PE routers that will transmit, receive, and load-balance traffic with flow labels.


We advise that you plan to configure these options during a maintenance window on those devices.

You can configure FAT flow label push and pop operations on the device at either the global routing instance level or at the individual interface level, as follows:

  1. Configure the EVPN routing instance of type evpn-vpws. For example:

    Verify the configuration:

  2. To configure FAT flow label push and pop operations at the evpn-vpws routing instance level:

    For example:

    Verify the configuration:

  3. Alternatively, to enable a specific interface in the evpn-vpws routing instance to push and pop FAT flow labels:

    For example:

    Verify the configuration:

Verify FAT Flow Labels Are Enabled

You can enter the show evpn vpws-instance CLI command to see if an evpn-vpws routing instance is configured to handle FAT flow labels. The output from this command displays Yes in the Flow-Label-Tx or Flow-Label-Rx output fields if you configured the device to insert or remove FAT flow labels on pseudowire traffic in the routing instance. These fields display No if FAT flow label operations are not enabled.