In a native FC storage-area network (SAN), physical FC switches and end devices (such as hosts with host bus adapters [HBAs]) are connected with fiber cable. The FC protocol runs natively on the SAN, and both the switches and end devices communicate through it.
With FCoE, that FC SAN is overlaid onto a physical Ethernet network, creating a VFC SAN running over Ethernet. In the previous section, we discussed the enhancements to Ethernet needed to facilitate this. In addition to these enhancements, a new process is needed on Cisco Nexus switches to support FC. This process is known as FCoE Manager or fcoe_mgr. The fcoe_mgr process controls all the FCoE components and configuration. The fcoe_mgr process is started by installing the FCoE feature set. Virtual SANs (VSANs) are then associated with designated FCoE VLANs and bind virtual Fibre Channel (vFC) interfaces to physical Ethernet interfaces. FCoE configuration is discussed later in this chapter.
With FCoE, HBAs are replaced with CNAs. CNAs enable converged I/O by supporting both FC and classical Ethernet data traffic on the same Ethernet wire. CNAs, along with proper drivers on the host end device, support FCoE.
Figure 9-9 is an illustration of a VSAN over Ethernet.
Figure 9-9 Virtual FC over Ethernet
The Fibre Channel portion of FCoE is configured with the help of a virtual Fibre Channel (vFC) interface. In FCoE, there are only physical Ethernet interfaces. You don’t have any physical Fibre Channel interfaces, so you actually need to create a logical instance of those Fibre Channel interfaces. To do that, you create a virtual Fibre Channel interface and bind it to both a VSAN that it’s associated with and a physical Ethernet interface on a switch, so that when that interface comes up, the vFC comes up. Logical Fibre Channel features can be configured on virtual Fibre Channel interfaces.
Following are some guidelines that you must follow when creating a virtual Fibre Channel interface:
Each virtual Fibre Channel interface must be bound to an FCoE-enabled Ethernet interface. FCoE is supported on 10-Gigabit Ethernet interfaces.
Each virtual Fibre Channel interface is associated with only one VSAN.
Any VSAN with associated virtual Fibre Channel interfaces must be mapped to a dedicated FCoE-enabled VLAN.
FCoE is not supported on private VLANs.
The Ethernet interface to which you bind the virtual Fibre Channel interface must be a trunk port. The FCoE VLAN that corresponds to the virtual Fibre Channel’s VSAN must be in the allowed VLAN list and must not be configured as the native VLAN of the trunk port. Also, the Ethernet interface must be configured as portfast using the spanning-tree port type edge trunk command.
Example 9-1 shows how to configure the VLAN on a physical Ethernet address, create virtual Fibre Channel interface 6, bind vFC 6 to the physical Ethernet interface, enable associated VLAN 600, and map VLAN 600 to VSAN 6.
Example 9-1 Virtual Fibre Channel Interface Configuration
switch# configure terminal
switch(config)# interface ethernet 1/2
switch(config-if)# switchport mode trunk
switch(config-if)# switchport trunk allowed vlan 1,600
switch(config)# interface vfc 6
switch(config-if)# bind interface ethernet 1/2
switch(config-if)# exit
switch(config)# vlan 600
switch(config-vlan)# fcoe vsan 6
switch(config-vlan)# exit
switch(config)# vsan database
switch(config-vsan)# vsan 6 interface vfc 6