Configuring FCoE on Nexus 5K

A simple FCoE topology with NPV/NPIV setup

Sample Configuration Steps on a FCoE supported Nexus 5k switch:-

Ensure FCoE license is installed on the switch. Confirm the same using 'show license usage' command. If missing, please install it using 

interface Ethernet1/1
  flowcontrol receive on
  flowcontrol send on

1. Configure a vfc interface

2. Allow a vsan on it.

3. Bind the interface to a physical interface 

4. In vsan database, add this vsan also to the interface vfc

The above steps completes vfc instantiation, allowing a vsan on the interface and add the vfc to a particular vsan in the database. Most importantly it binds the vfc to a physical interface as well.

Lastly, create a FCoE vlan, and map the vlan to a vsan as well.

Port flap on the vfc and/or physical interface may be required to bring up the vfc interface.

References :- A very detailed explanation of various topologies supported in FCoE NPV is mentioned in here and here

Fabric Interconnect Operation Modes

Fabric Interconnect Modes of Operation

There is no local switching on IOM/FEX ever, FI switches veth's traffic which are locally present on it and utilizes an uplink switch to switch traffic to the veths defined on the corresponding FI for inter-host (within chassis) communication.

End Host Mode (EHM): - 

1. Default mode for FI. FI doesn't learn any MACs from upstream ports. Only learns MACs southbound from connected blades/racks (server ports). In this mode the switch is exposed to upstream switches as a host and not as a switch. 
2. RPF check. It ensures that traffic ingress from northbound switch to FI is coming to the correct FI uplink interface to which the downstream blade vifs are bound to. else, it's dropped. This ensures again that there are no duplicate packets sent back to the blade's vifs from the remote host.
3. Deja vu check. Looped packet back from another adjacent port/s within the same FI ? If yes, this will be dropped at the FI itself. For instance, a broadcast packet from the blade might loop back to another uplink port into the chassis again and can result in creating an unwanted broadcast storm. Since the FI has track of the packet being seen on a different port earlier, it will promptly drop it.
4. No STP and hence no blocked ports. All ports can forward traffic.
5. Designated Broadcast/Multicast up-link port. for receiving traffic (G pin port).