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Converting an Ethernet Interface To a Fibre Channel Interface

When a QFX3500 acts as an FCoE-FC gateway, native Fibre Channel (FC) traffic flows between the switch and the storage area network (SAN) FC switch. When you configure a port as an FC interface, it transports only FC traffic. It does not transport Ethernet traffic.

You can configure ports xe-0/0/0 through xe-0/0/5 as fc-0/0/0 through fc-0/0/5 and ports xe-0/0/42 through xe-0/0/47 as fc-0/0/42 through fc-0/0/47 to create blocks of native FC interfaces.

Each of these blocks of ports must be configured either as all Ethernet ports or as all native FC ports. Within each block of ports, you cannot mix FC and Ethernet interfaces. This means that you can configure 0, 6, or 12 ports as native FC ports. Configuring a Physical Fibre Channel Interface describes how to configure the port blocks as physical FC interfaces.


Do not configure ports that you want to use for native FC traffic as part of an Ethernet VLAN or as Ethernet ports.

Configure a port as an FC interface when the port connects to the F_Port of an FC switch.

FC interface configuration includes:

  • Explicitly specifying one or more ports as an FC family interface in NP_Port mode (mandatory).

  • Configuring the FC interface options port speed and buffer-to-buffer credit state change number (BB_SC_N) (optional).

  • Configuring the interface as a loopback interface (optional).

The buffer-to-buffer state change number feature prevents the loss of buffer-to-buffer credits between the two interfaces on either end of an FC link. The state change number determines the number of frames and receiver ready (R_RDY) primitives the interfaces exchange between the state change send (BB_SCs) and the state change receive (BB_SCr) primitives used to track these transactions.

Enabling BB_SC_N by configuring BB_SC_N on both of the FC link interfaces:

  • Requests that 2BB_SC_N number of frames be sent between two consecutive BB_SCs primitives, and

  • Requests that 2BB_SC_N number of R_RDY primitives be sent between two consecutive BB_SCr primitives.

When the number of R_RDY primitives received equals 2BB_SC_N, the R_RDY counter resets to zero. When the number of frames received equals 2BB_SC_N, the frame counter resets to zero. The interfaces calculate the number of buffer-to-buffer credits lost based on counter discrepancies and take corrective action to recover the lost credits.

If you enable BB_SC_N, the recommended BB_SC_N setting is eight. Setting the BB_SC_N number to zero (0) disables the feature. If either of the two connected FC interfaces is configured with zero as the BB_SC_N value, then both interfaces disable the feature. If the two connected FC interfaces have different nonzero BB_SC_N numbers configured, both interfaces use the higher number.

For the port to transport FC traffic, you must also set the physical port as an FC port using the port-range command.

To configure an FC interface using the CLI:

  1. Specify the interface as family FC and set the port mode to NP_Port (setting the port mode to NP_Port is a mandatory configuration):

    For example, to configure the interface fc-0/0/3 as an FC interface and set the port mode to np-port:

  2. Configure the FC interface speed option:

    For example, to set the FC interface speed option to 8g for the interface fc-0/0/3:

    The default port mode is auto-negotiation, which sets the port speed to match the speed of the attached FC F_Port interface (2 Gbps, 4 Gbps, or 8 Gbps).

  3. Configure the optional buffer-to-buffer credit state change number:

    For example, to set the FC interface buffer-to-buffer credit state change number to 8 for the interface fc-0/0/3:

After you configure one or more FC interfaces, assign them and an FCoE VLAN to an FC fabric.