Cisco MDS SanOS Troubleshooting Guide -- Troubleshooting N-Port Virtualization

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This section describes how to identify and resolve problems that can occur with N-Port virtualization.



N-Port virtualization (NPV) reduces the number of Fibre Channel domain IDs in SANs. Switches operating in the NPV mode do not join a fabric; rather, they pass traffic between NPV core switch links and end-devices, which eliminates the domain IDs for these edge switches.

Note Note: NPV is available only for the following Cisco MDS 9000 switches: the Cisco MDS 9124 Multilayer Fabric Switch, the Cisco MDS 9134 Fabric Switch, the Cisco Fabric Switch for HP c-Class BladeSystem and the Cisco Fabric Switch for IBM BladeCenter.

NPV makes a Fabric or Blade switch appear as a host to the core Fibre Channel switch, and as a Fibre Channel switch to the servers in the Fabric or Blade switch. NPV aggregates multiple locally-connected N-ports into one or more external NP links, thereby sharing the domain ID of the NPV core switch among multiple NPV switches. NPV also allows multiple devices to attach to same port on the NPV core switch.

NPV makes use of N port identifier virtualization (NPIV) to get multiple FCIDs allocated from the core switch on the NP-port.

A switch is in NPV mode after a user has enabled NPV and the switch has successfully rebooted. NPV mode applies to an entire switch. All end devices connected to a switch that is in NPV mode must log in as an N-port to utilize this feature (loop-attached devices are not supported). All links from the edge switches (in NPV mode) to the NPV core switches are established as NP-ports. NPIV is used by the switches in NPV mode to log in to multiple end-devices that share a link to the NPV core switch.

For a complete description of NPV, refer to the Cisco MDS 9000 Family CLI Configuration Guide.

Initial Troubleshooting Checklist

Troubleshooting an NPV problem involves gathering information about the switch configuration and connectivity of individual devices and the entire SAN fabric. Begin your troubleshooting activity as follows:


Check off

Verify that the NPV core switch supports NPIV and that NPIV is enabled.

Verify that NPV is enabled on the NPV device.

Verify that the ports are properly connected.

For all NPV core switch links, ensure that the port mode on the NPV device is NP Port, and ensure that the port mode on the NPV core switch is F Port.

Ensure that the VSAN values configured on both sides of NPV core switch link are the same.

For all the device links, ensure that the port mode on the NPV device is F port.

Ensure that the VSAN value configured on the device links is correct.

Verify the status of servers and external interfaces, using the show npv status command.

Limitations and Restrictions

  • NPV core switches must support NPIV.
  • You cannot manually assign the server interfaces to a specific NPV core switch link. If an NPIV capable module is connected to the server interface, all the logins from the NPIV capable module will use the same NPIV core switch link.
  • Remote SPAN is not supported.
  • A maximum of 16 VSANs are supported on an NPV device.
  • Local switching is not supported; rather, all traffic is switched via the NPV core switch.
  • Only F, NP, and SD ports are supported in NPV mode.
  • CFS and QoS are not supported.
  • IVR, SDV and FICON are not supported.
  • If an NPV link failover occurs, servers that are booted over the SAN with NPV will temporarily lose access to their boot LUNs.

Common CLI Commands for NPV

Note Note: Because the output is based on name server database information, the show fcns database npv commands can be run from any MDS switch running SAN-OS 3.2(1) or later. The switch does not need to be NPV enabled.

Common Problems with NPV

Moving the Login of an End Device

NPIV Is Not Enabled

VSAN Mismatches

Core NPV Device Is Not a Switch

NPV Core Switch Port Is Down

Server Interface is Down

Waiting on FLOGI from the Server or Target

Waiting on External Link to Come Up

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