Fibre Channel over Ethernet (FCoE) encapsulation allows a physical Ethernet cable to simultaneously carry Fibre Channel and Ethernet traffic. In Cisco Nexus devices, an FCoE-capable physical Ethernet interface can carry traffic for one virtual Fibre Channel (vFC) interface.

Like any interface in Cisco NX-OS, vFC interfaces are manipulable objects with properties such as configuration and state. Native Fibre Channel and vFC interfaces are configured using the same CLI commands.

The following capabilities are not supported for virtual Fibre Channel interfaces:

• SAN port channels.

• The SPAN destination cannot be a vFC interface.

• Buffer-to-buffer credits.

• Exchange link parameters (ELP).

• Configuration of physical attributes (speed, rate, mode, transmitter information, MTU size).

• Port tracking.

Each physical Fibre Channel interface in a switch may operate in one of several port modes: E mode, TE mode, F mode, and TF mode. A physical Fibre Channel interface can be configured as an E port or an F port, an F port, or an SD port. Interfaces may also be configured in Auto mode; the port type is determined during interface initialization.

Fibre Channel interfaces may operate in E mode or an F mode.

Virtual Fibre Channel interfaces can be configured in E mode or F mode.

Interfaces are automatically assigned VSAN 1 by default.

Each interface has an associated administrative configuration and an operational status:

• The administrative configuration does not change unless you modify it. This configuration has various attributes that you can configure in administrative mode.

• The operational status represents the current status of a specified attribute such as the interface speed. This status cannot be changed and is read-only. Some values may not be valid when the interface is down (for example, the operational speed).

The interface state depends on the administrative configuration of the interface and the dynamic state of the physical link.

Buffer-to-buffer credits (BB_credits) are a flow-control mechanism to ensure that Fibre Channel interfaces do not drop frames. BB_credits are negotiated on a per-hop basis.

The BB_credit mechanism is used on Fibre Channel interfaces but not on virtual Fibre Channel interfaces. The receive BB_credit determines the receive buffering capability on the receive side without having to acknowledge the peer. This is important for links with large bandwidth-delays (long links with large latency) to be able to sustain line-rate traffic with increased latency.

For virtual Fibre Channel interfaces, BB_credits are not used. Virtual Fibre Channel interfaces provide flow control based on a class based pause mechanism named Priority Flow Control.Priority-Flow_control.

Note

Buffer-to-buffer (B2B) credits are not configurable. Fill pattern in the 8G links must be IDLE. You must set the fill pattern in the 8G links to IDLE on both the peers. Use the command switchport fill-pattern IDLE speed speed to set the fill pattern to IDLE on Cisco Nexus 9000 switches. switch (config)# interface fc1/1 switch (config-if)# switchport fill-pattern IDLE speed 8000

Note	The receive BB_credit value is 64 in N9K-C93180YC-FX and 32 in N9K-C93360YC-FX2 and N9K-C9336C-FX2-E. This is applicable for all port modes (F,E) in both platforms and cannot be changed.

Ensure that you have the correct license installed before using Fibre Channel interfaces and capabilities. For more information on licensing, see Enabling FC/FCoE chapter in this guide.

Configuring QoS Policies for FC/FCoE

• There are four types of FC/FCoE default policies: network-qos, output queuing, input queuing, and input qos.

• To use a different queue or cos value for FC/FCoE traffic, create user-defined policies.

• You can configure a QoS policy by following one of these methods:

  • Predefined policies—You can apply a predefined QoS policy: default-fcoe-in-policy .

    Note	No policy will be applied by default for FCoE. We recommend to apply no-stats to QoS policy.

  • User-defined policy—You can create a QoS policy that conforms to one of the system-defined policies.

Configuring System-wide QoS Policy

Note	The network-qos policy and output/input queuing policies should be applied at the system level and the qos policy should be applied at the interface level, for every interface that carries the FC/FCoE traffic.

switch(config)# system qos
switch(config-sys-qos)# service-policy type queuing input default-fcoe-in-que-policy
switch(config-sys-qos)# service-policy type queuing output { default-fcoe-8q-out-policy | default-fcoe-out-policy }
switch(config-sys-qos)# service-policy type network-qos { default-fcoe-8q-nq-policy | default-fcoe-nq-policy }

Configuration Example for user-defined policies

switch(config)# policy-map type network-qos fcoe_nq
switch(config-pmap-nqos)# class type network-qos c-nq1
switch(config-pmap-nqos-c)# pause pfc-cos 3
switch(config-pmap-nqos-c)# mtu 9216
switch(config-pmap-nqos-c)# class type network-qos c-nq2
switch(config-pmap-nqos-c)# mtu 1500
switch(config-pmap-nqos-c)# class type network-qos c-nq3
switch(config-pmap-nqos-c)# mtu 1500
switch(config-pmap-nqos-c)# class type network-qos c-nq-default
switch(config-pmap-nqos-c)# mtu 1500
switch(config-pmap-nqos-c)# exit
switch(config-pmap-nqos)# exit
switch(config)#
switch(config)# policy-map type queuing fcoe-in-policy
switch(config-pmap-que)# class type queuing c-in-q1
switch(config-pmap-c-que)# bandwidth percent 50
switch(config-pmap-c-que)# class type queuing c-in-q-default
switch(config-pmap-c-que)# bandwidth percent 50
switch(config-pmap-c-que)# exit
switch(config)
switch(config)# policy-map type queuing fcoe-out-policy
switch(config-pmap-que)# class type queuing c-out-q3
switch(config-pmap-c-que)# priority level 1
switch(config-pmap-c-que)# class type queuing c-out-q-default
switch(config-pmap-c-que)# bandwidth remaining percent 50
switch(config-pmap-c-que)# class type queuing c-out-q1
switch(config-pmap-c-que)# bandwidth remaining percent 50
switch(config-pmap-c-que)# class type queuing c-out-q2
switch(config-pmap-c-que)# bandwidth remaining percent 0
switch(config-pmap-c-que)# exit
switch(config)#
switch(config)# class-map type qos match-any fcoe
switch(config-cmap-qos)# match protocol fcoe
switch(config-cmap-qos)# match cos 3
switch(config-cmap-qos)# exit
switch(config)#
switch(config)# policy-map type qos fcoe_qos_policy
switch(config-pmap-qos)# class fcoe
switch(config-pmap-c-qos)# set cos 3
switch(config-pmap-c-qos)# set qos-group 1
switch(config-pmap-c-qos)# exit
switch(config-pmap-qos)# exit
switch(config)#
switch(config)# system qos
switch(config-sys-qos)# service-policy type queuing input fcoe-in-policy 
switch(config-sys-qos)# service-policy type queuing output fcoe-out-policy 
switch(config-sys-qos)# service-policy type network-qos fcoe_nq

Note	The set cos 3 command under the QOS policy is mandatory only when there are native fiber channel ports and the command is applicable only for N9K-C93180YC-FX platform , N9K-C93360YC-FX2 platforms . For all the other Cisco Nexus 9000 Platform switches, this step is optional.

Applying the ingress QoS policy to each Ethernet/port-channel interface that is bound to vFC interface for FC/FCoE.

switch(config)# interface ethernet 2/1
switch(config-if)# switchport mode trunk
switch(config-if)# mtu 9216 /* Or maximum allowed value */
switch(config-if)# service-policy type qos input { default-fcoe-in-policy | fcoe_qos_policy )  no-stats
switch(config-if)# exit
switch(config)#

• Configuring FC/FCoE QoS policies

  • There are four types of FC/FCoE default policies: network QoS, output queuing, input queuing, and QoS.

  • To use a different queue or cos value for FC/FCoE traffic, create user-defined policies.

• Configuring Network QoS Policies for FC/FCoE

  • You can configure a network QoS policy by following one of these methods:

    • Predefined policies—You can apply a predefined network QoS policy that fits your requirement. You have the option to choose either default-fcoe-8q-nq-policy or default-fcoe-nq-policy .

      Note	No policy will be applied by default for FC/FCoE.

    • User-defined policy—You can create a network QoS policy that conforms to one of the system-defined policies.

• Configuring Output Queuing Policies for FC/FCoE

  • You can configure an output queuing policy by following one of these methods:

    • Predefined policies—You can apply a predefined output queuing policy that fits your requirement. You have the option to choose either default-fcoe-8q-out-policy or default-fcoe-out-policy .

      Note	No policy will be applied by default for FC/FCoE.

    • User-defined policy—You can create a output queuing policy that conforms to one of the system-defined policies.

• Configuring Input Queuing Policies for FC/FCoE

  • You can configure an input queuing policy by following one of these methods:

    • Predefined policies—You can apply a predefined input queuing policy: default-fcoe-in-que-policy .

      Note	No policy will be applied by default for FCoE.

    • User-defined policy—You can create a input queuing policy that conforms to one of the system-defined policies.

Note	Whenever you see label allocation failure in the syslog, there is a possibility of FC/FCoE ACL not getting applied on interfaces. You must then check whether the QoS policy is applied with no-stats on the interfaces.

Cisco Nexus C93180YC-FX and C93360YC-FX2 switches support up to 48 and 96 physical fibre channel (FC) interfaces respectively as either uplinks connected to SAN network or as downlinks (connected to server or target). Cisco Nexus N9K-C9336C-FX2-E switches can have up to 112 physical fibre channel (FC) breakout interfaces as either uplinks connected to SAN network or as downlinks (connected to server or target). Only ports from 9 to 36 can be converted in FC breakout.

Each Fibre Channel port can be used as a downlink (connected to a server) or as an uplink (connected to the data center SAN network). The Fibre Channel interfaces support the following modes: E, F, SD, TE, and TF.

N port identifier virtualization (NPIV) provides a means to assign multiple FC IDs to a single N port. This feature allows multiple applications on the N port to use different identifiers and allows access control, zoning, and port security to be implemented at the application level. The following figure shows an example application using NPIV.

The SFP transmitter type can be displayed for a physical Fibre Channel interface (but not for a virtual Fibre Channel).

The small form-factor pluggable (SFP) hardware transmitters are identified by their acronyms when displayed in the show interface brief command. If the related SFP has a Cisco-assigned extended ID, then the show interface and show interface brief commands display the ID instead of the transmitter type. The show interface transceiver command and the show interface fc slot/port transceiver command display both values for Cisco supported SFPs.

The show interface command displays interface configurations. If no arguments are provided, this command displays the information for all the configured interfaces in the switch.

You can also specify arguments (a range of interfaces or multiple, specified interfaces) to display interface information. You can specify a range of interfaces by entering a command with the following example format: interface fc2/1 - 4 , fc3/2 - 3

The following example shows how to display all interfaces:

switch# show interface

fc3/1 is up
...
fc3/3 is up
...
Ethernet1/3 is up
...
mgmt0 is up
...
vethernet1/1 is up
...
vfc 1 is up

The following example shows how to display multiple specified interfaces:

switch# show interface fc3/1 , fc3/3
fc3/1 is up
...
fc3/3 is up
...

The following example shows how to display a specific interface:

switch# show interface vfc 1

vfc 1 is up

...

The following example shows how to display interface descriptions:

switch# show interface description
-------------------------------------------------
Interface          Description
-------------------------------------------------
fc3/1              test intest
Ethernet1/1              --
vfc 1              --
...

The following example shows how to display all interfaces in brief:

switch# show interface brief

The following example shows how to display interface counters:

switch# show interface counters

The following example shows how to display transceiver information for a specific interface:

switch# show interface fc3/1 transceiver

Note	The show interface transceiver command is only valid if the SFP is present.

The show running-configurationshow running-config command displays the entire running configuration with information for all interfaces. The interfaces have multiple entries in the configuration files to ensure that the interface configuration commands execute in the correct order when the switch reloads. If you display the running configuration for a specific interface, all the configuration commands for that interface are grouped together.

The following example shows the interface display when showing the running configuration for all interfaces:

switch# show running configurationshow running-config
...
interface fc3/5
  switchport speed 200016000
...
interface fc3/5
  switchport mode E 
...
interface fc3/5
  channel-group 11 force
  no shutdown

The following example shows the interface display when showing the running configuration for a specific interface:

switch# show running configuration fc3/5show running-config fc3/5
interface fc3/5
  switchport speed 200016000
  switchport mode E
  channel-group 11 force
  no shutdown

The following example shows how to display the BB_credit information for all Fibre Channel interfaces:

switch# show interface fc1/7
...
fc1/7 is up
Hardware is Fibre Channel, SFP is short wave laser w/o OFC (SN)
Port WWN is 20:07:2c:d0:2d:50:e5:24
Admin port mode is auto, trunk mode is off
snmp link state traps are enabled
Port mode is F, FCID is 0xe10280
Port vsan is 500
Operating Speed is 32 Gbps
Admin Speed is auto
Transmit B2B Credit is 12
Receive B2B Credit is 64
Receive data field Size is 2112
Beacon is turned off
fec state is enabled by default
5 minutes input rate 0 bits/sec,0 bytes/sec, 0 frames/sec
5 minutes output rate 0 bits/sec,0 bytes/sec, 0 frames/sec
16705 frames input,1225588 bytes
0 discards,0 errors
0 invalid CRC/FCS,0 unknown class
0 too long,0 too short
16714 frames output,1345676 bytes
0 discards,0 errors
0 input OLS,0 LRR,0 NOS,0 loop inits
7 output OLS,4 LRR, 0 NOS, 0 loop inits
Receive B2B Credit performance buffers is 0
12 transmit B2B credit remaining
0 low priority transmit B2B credit remaining
Interface last changed at Thu Nov 14 11:59:40 2019