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Disabling the Control Word for Layer 2 VPNs

A 4-byte control word provides support for the emulated VC encapsulation for Layer 2 VPNs. This control word is added between the Layer 2 protocol data unit (PDU) being transported and the VC label that is used for demultiplexing. Various networking formats (ATM, Frame Relay, Ethernet, and so on) use the control word in a variety of ways.

On networks with equipment that does not support the control word, you can disable it by including the no-control-word statement:

You can include this statement at the following hierarchy levels:

  • [edit routing-instances routing-instance-name protocols l2vpn]

  • [edit logical-systems logical-system-name routing-instances routing-instance-name protocols l2vpn]

For more information about configuring the control word, see Configuring the Control Word for Layer 2 Circuits and the Layer 2 Circuits User Guide.


Use the no-control-word statement to disable the control word when the topology uses generic routing encapsulation (GRE) as the connection mechanism between PEs, and one of the PEs is an M Series router.