Configuring a Control Word for BGP VPLS

 

In a BGP VPLS network, transit routers must determine the payload for hash calculations for load balancing. While parsing an MPLS encapsulated packet for hashing, a transit router can incorrectly calculate an Ethernet payload as an IPv4 or IPv6 payload if the first nibble of the destination address MAC is 0x4 or 0x6, respectively. This false positive can cause out-of-order packet delivery over a pseudowire. This issue can be avoided by configuring a BGP VPLS PE router to request that other BGP VPLS edge (VE) routers insert a control word between the label stack and the MPLS payload.

Warning

If you attempt to set a control word in a VPLS network that contains a VE router that does not support a control word, the pseudowire will not come up. To ensure that the pseudowire comes up, be sure that all VE routers in the VPLS network support the presence of a control word.

Before configuring support for a control word in a BGP VPLS network, ensure that the router meets the following requirements:

  • MX Series router running Junos OS Release 14.1 or later and containing one of the following Flexible PIC Concentrators: ADPC, NPC, or I-Chip

    OR

  • M320 router running Junos OS Release 14.1 or later and containing either the I-Chip or the Trio

To configure a VE router to expect a control word between the label stack and the MPLS payload:

  1. At the [edit routing-instances] hierarchy level in configuration mode, set control-word for the VPLS protocol for the specified routing instance.

    For example:

  2. If you are setting control-word on a Trio-based MPC on an MX Series router, set no-ether-pseudowire to omit the IP payload over the Ethernet pseudowire from the hash key.
  3. Verify the configuration.
  4. Repeat the configuration on each VE router in the BGP VPLS network.
  5. Run show vpls connections instance routing-instance-name extensive to verify the presence of a control word for the pseudowire.

    For example:

    user@host# show vpls connections instance vpls1 extensive

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