NPV and Forwarding Mechanism

[visitor68]

Hi -

From my understanding, an FCoE switch is an FCF if it de-encapsulates the FC frame from the FCoE frame and makes a forwarding decision based on the destination FC_ID in the FC header. FSPF will decide what the next hop is. Subsequently, the FCoE frame will either be forwarded out an FC port or re-encapsulated into an FCoE frame.

Does an FCoE switch in NPV mode make forwarding decsions based on destination FC-ID using FSPF?

Collolary: is an FCoE switch in NPV mode an FCF based on the definiton above?

[richbarb]

Hello,

FSPF not run on npv switch mode, then it is not a FCF device, FCF will be the upstream device. To forward frames the npv switch just does pinning.

In the FCoE npv device, the port-channel load-balance will follow the rules of ethernet port-channel load-balance. In this case only Layer-2 information is avaliable.

[visitor68]

Rich, not sure I totally agree with you. The definition of an FCF, as I understand it and as defined by a leading FC expert, Robert Kembel, is a device that will de-encapsulate an FCoE frame and make a forwarding decision based on the D_ID in the FC frame header. So the question is what mechanism does the FCoE switch in NPV mode use to forward frames?

[richbarb]

Hello visitor68,

It's interesting questioning.

If you take a look in Cisco documentation you will see a clear separation of npv switch mode and a FCF switch (That always will be the switch that can handle FC frames header).

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/san_switching/513_n1_1/b_Cisco_n5k_nxos_sanswitching_config_guide_rel513_n1_1_chapter_0110.html

Keep in mind that a npv switch does is mapping one port to another, It's no take decisions based on header frame or does encapsulation/desencapsulation. The host depends completly of NPIV upstream switch to FIP works and bring up the vfc interface.

The mechanism is simple, just mapping TF ports to VNP ports in the same vsan to forward all frames. If more than one VNP in the same vsan is avaliable the rebalancing will occur by default or can be done manually if you wish.

The documentation is not so clear about definitions or concepts, but about the "data plane decisions" is clear enough.

http://www.cisco.com/en/US/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli_rel_4_0_1a/npv.html#wp1522810

Regards.