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Cisco NX-OS and Cisco Nexus Switching: Unified Fabric

Chapter Description

This chapter shows the basic Nexus 5x00 and Nexus 7000 configurations necessary to provide a Unified access method for LAN data traffic and SAN storage traffic. The multiple technologies that can be used with Unified Fabric such as NPV, NPIV FCOE-NPV, Storage VDCs, and shared interfaces are illustrated, and various use cases are discussed.

N-Port Virtualization

The fibre channel module of the Nexus 5x00 series switch can operate in two modes:

  • Fabric
  • NPV (N-Port Virtualization)

When in fabric mode, the switch module operates as any switch in a fibre channel network does.

Fabric mode switches have the following characteristics:

  • Unique domain ID per virtual storage area network (VSAN)
  • Participation in all domain services (zoning, fabric security, Fibre Channel Identification [FCID] allocation, and so on)
  • Support for interoperability modes

When the fibre channel module is configured in NPV mode, it does not operate as a typical fibre channel switch; instead leveraging a service, NPIV, on the upstream or core fibre channel switch for domain services. The switch operates in a similar fashion as an NPIV-enabled host on the fabric. The advantage NPV provides the network administrator is the control of domain IDs and points of management on a fibre channel network as it scales.

Additional benefits of NPV include the capability to manage the fibre channel switch as a discrete entity for tasks such as software management and debugging the fibre channel network. NPV also enables network administrators to connect FCoE hosts to non–FCoE-enabled SANs and simplifies third-party interoperability concerns because the NPV enabled fibre channel module does not participate in domain operations or perform local switching. This enables multivendor topologies to be implemented without the restrictions the interoperability mode requires.

The fibre channel module in the Nexus 5x00 creates a new port type to the fibre channel network when in NPV mode: the NP-port. The NP-port proxies fabric login (FLOGI) requests from end stations and converts them to Fabric Discoveries (FDISC) dynamically and transparently to the end device. The result is that end systems see the NPV-enabled switch as a Fabric Port (F-port) and the upstream/core switch sees the NPV-enabled switch as an F-port as well. Figure 8-9 illustrates the port roles used in an NPV-enabled network.

Figure 8-9

Figure 8-9. Port Roles in an NPV-Enabled Network

N-Port Identification Virtualization

A key component to enable the proper operation of NPV is the need for N-Port Identification Virtualization (NPIV) on the core/upstream fibre channel switch. NPIV is an industry-standard technology defined by the T11 committee as part of the Fibre Channel Link Services (FC-LS) specification and enables multiple N Port IDs or FCIDs to share a single physical N Port. Prior to NPIV, it was not possible to have a system that used multiple logins per physical port—it was a one-login-to-one-port mapping. With the increasing adoption of technologies such as virtualization, the need to allow multiple logins was created. NPIV operates by using Fabric Discovery (FDISC) requests to obtain additional FCIDs.


Building on Fibre Channel NPV mode, the Nexus 5x00 supports running in FCoE-NPV mode as well. FCoE-NPV brings similar benefits as the Fibre Channel NPV mode to a pure FCoE implementation. The switch still uses FIP snooping to determine FCoE traffic and to maintain separation and provide security with the benefits of minimized domain sprawl, simplified management, and fewer FCoE devices to manage. FCoE NPV also creates a new port type for the VNP (Virtual NPV Port). Figure 8-10 illustrates where the VNP port resides in an FCoE NPV topology.

Figure 8-10

Figure 8-10. FCoE NPV Topology

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