Layer 2 control protocols

SR OS has awareness of multiple Layer 2 Control Protocols (L2CP). In some configurations, these L2CP frames are extracted and processed by the receiving SR. But there are some deployments where it is desirable to have the SR transparently forward the L2CP frames through a Layer 2 VLL or VPLS service. The SR OS support for this transparent tunnelling is configured on a protocol basis as described in this section.

L2CP frames are processed as follows:

  • tunneled

    SR OS passes the frames through any associated service.

  • peered

    SR OS extracts and processes the frame.

  • discarded

    SR OS extracts the frame and then discards it.

The following L2CP frames are always tunneled:
  • STP/RSTP/MSTP (assuming Spanning Tree is not enabled if the ingress SAP is attached to a VPLS service)

  • LAMP

  • MAC Specific Control Protocols

  • Provider Bridge Group Address

  • Provider Bridge MVRP Address

Other frame types are processed according to CLI configuration, as follows:
  • PAUSE frames

    PAUSE frames are transmitted to request backward direction flow control. By default, SR OS peers these frames on reception and pauses the transmit side of the port. On some ports, this behavior can be changed to discard these frames by using the config>port>ethernet discard-rx-pause-frames CLI command.

    PAUSE frames are never tunneled.

    PAUSE frames are identified as frames with Ethertype (0x8808).

  • LACP frames

    If the port is part of a LAG, the LACP frames are peered. If the port is not part of a LAG, the LACP frames are discarded or tunneled according to the configuration of the config>port>ethernet lacp-tunnel CLI command.

    LACP frames are identified as frames with Ethertype (0x8809) and the slow-protocol subtype (0x01)

  • EFM-OAM frames

    If the port has EFM-OAM processing enabled, the EFM-OAM frames are peered. If EFM-OAM processing is not enabled on the port, the EFM-OAM frames are discarded or tunneled according to the configuration of the config>port>ethernet lacp-tunnel CLI command.

    EFM-OAM frames are identified as frames with Ethertype (0x8809) and the slow-protocol sub-type (0x03).

  • ESMC frames

    If the port is an input reference to the central frequency clock, the ESMC frames are peered. If the port is not an input reference to the central frequency clock, the ESMC frames are discarded. To override the preceding scenarios and tunnel the ESMC frames, configure the config>port>ethernet>ssm esmc-tunnel CLI command.

    ESMC frames are identified as frames with Ethertype (0x8809) and the slow-protocol sub-type (0x0A).

  • 802.1x frames

    By default, the 802.1x frames are extracted when they are received. For extracted frames, if a RADIUS server is configured, the frames are peered; otherwise they are discarded. The extraction can be overridden and the 802.1x frames can be tunneled by using the config>port>ethernet>dot1x tunneling CLI command.

    802.1x frames are identified as frames with Ethertype (0x888E).

  • E-LMI frames

    If Ethernet Local Management Interface (E-LMI) processing is enabled on the port, E-LMI frames are peered. Otherwise, the E-LMI frames are dropped from VPLS and tunneled for Epipe.

    E-LMI frames are identified as frames with Ethertype (0x88EE) and a destination MAC address of 01:80:C2:00:00:07.

  • LLDP frames

    If LLDP processing is enabled on the port, LLDP frames are peered. Otherwise, LLDP frames are discarded or tunneled according to the configuration of the config>port>ethernet>lldp>dst-mac tunnel-nearest-bridge CLI command.

    LLDP frames are identified as frames with Ethertype (0x88CC) and destination MAC address of 01-80-C2-00-00-0E.

  • PTP peer delay frames

    If the port is configured in the router as an active port within the PTP process, the frames are peered; otherwise, the frames are tunneled.

    PTP message frames are identified as frames with Ethertype (0x88F7).

The maximum transparency of L2CP frames is achieved by configuring the following CLI commands on the port:
config port ethernet 
  discard-rx-pause-frames
  lacp-tunnel
  efm-oam tunnelling
  ssm esmc-tunnel
  dot1x tunneling
  lldp dst-mac tunnel-nearest-bridge
Note: E-LMI must be disabled and the port must not be configured as a PTP port.