NPIV and NPV – Cisco CCNP and CCIE

In fabric mode, the NX-OS switches provide the standard Fibre Channel switching capability and features. In this mode, each switch that joins a SAN is assigned a domain ID. Each SAN (or VSAN) supports a maximum of 239 domain IDs, so the SAN has a limit of 239 switches. In a SAN topology with a large number of edge switches, the SAN may need to grow beyond this limit. N port virtualization (NPV) alleviates the domain ID limit by sharing the domain ID of the core switch among multiple edge switches.

The NPV core switch, with the N port identifier virtualization (NPIV) feature enabled, provides a means to assign multiple FCIDs 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.

An NPV edge switch relays all traffic from server-side ports to the core switch. The core switch provides F port functionality (such as login and port security) and all the Fibre Channel switching capabilities. The edge switch shares the domain ID of the core switch. The edge switch appears as a Fibre Channel host to the core switch and as a regular Fibre Channel switch to its connected devices.

Figure 8-39 shows an interface-level view of an NPV configuration.

Figure 8-39 NPV Interface Configuration

In NPV mode, a subset of fabric mode CLI commands and functionality is supported. For example, commands related to fabric login and name server registration are not required on the edge switch because these functions are provided in the core switch. To display the fabric login and name server registration databases, you must enter the show flogi database and show fcns database commands on the core switch.

All interfaces from the edge switch to the core switch are configured as proxy N ports (NP ports). An NP uplink is a connection from an NP port on the edge switch to an F port on the core switch. When an NP uplink is established, the edge switch sends a fabric login message (FLOGI) to the core switch, and then (if the FLOGI is successful) it registers itself with the name server on the core switch. Subsequent FLOGIs from end devices connected to this NP uplink are converted to fabric discovery messages (FDISCs). In Cisco Nexus devices, NP uplink interfaces must be native Fibre Channel interfaces.

When an NP port becomes operational, the switch first logs itself in to the core switch by sending an FLOGI request (using the port WWN of the NP port). After completing the FLOGI request, the switch registers itself with the fabric name server on the core switch (using the symbolic port name of the NP port and the IP address of the edge switch).

Server interfaces are F ports on the edge switch that connect to the servers. A server interface may support multiple end devices by enabling the N port identifier virtualization (NPIV) feature on the core switch. NPIV provides a means to assign multiple FCIDs to a single N port, which allows the server to assign unique FCIDs to different applications. To use the NPIV feature, you have to enable the NPIV feature. Server interfaces are automatically distributed among the NP uplinks to the core switch. All of the end devices connected to a server interface are mapped to the same NP uplink. In Cisco Nexus devices, server interfaces can be physical or virtual Fibre Channel interfaces.

Note

Zoning is not enforced at the edge switch (rather, it is enforced on the core switch). Multiple devices attached to an edge switch log in through the same F port on the core, so they cannot be separated into different zones.

When you enable NPV on an edge switch using the npv enable command, the system configuration is erased and the switch reboots. After you enable NPV, you should configure the NP uplink interfaces and the server interfaces using the switchport mode NP and switchport mode F commands, respectively. You cannot configure NPV mode on a per-interface basis. NPV mode applies to the entire switch.

On NPV switches, by default, trunk mode is disabled. You can configure trunk mode as on (enabled), off (disabled), or auto (automatic). The trunk mode configuration at the two ends of an ISL, between two switches, determine the trunking state of the link and the port modes at both ends as listed in Table 8-21.

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