C H A P T E R 1 Troubleshooting Overview; Basics; Basic Connectivity; Fibre Channel End-To-End Connectivity - Cisco MDS 9000 Series Troubleshooting Manual

Introduction
S e n d c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m .
LUNs, (but not all of them) on an existing subsystem, then fabric-specific issues (FSPF, ISLs, FCNS) do
not need to be investigated, as they are currently working correctly. The fabric components can therefore
be eliminated from the problem.
By answering the questions in the following subsections, you can determine the paths you need to follow
and the components that you should investigate further. These questions are independent of host, switch
or subsystem vendor.

Basics

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Basic Connectivity

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Examine the FLOGI database on the two switches that are directly connected to the host HBA and
subsystem ports. Also, verify that both ports (attached port on MDS-A and MDS-B) are members of the
same VSAN. If both devices are listed in the FCNS database then ISLs are not an issue.

Fibre Channel End-to-End Connectivity

Answering the following questions will help to determine if end-to-end fibre channel connectivity exists
from a host or subsystem perspective:
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Cisco MDS 9000 Family Troubleshooting Guide
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Is this a newly installed system or an existing installation? (It could be a new SAN, host or
subsystem, or new LUNs exported to an existing host.)
Has the host ever been able to see its storage?
Does the host recognize any LUNs in the subsystem?
Are you trying to solve an existing application problem (too slow, too high latency, excessively long
response time) or did the problem show up recently?
What changed in the configuration or in the overall infrastructure immediately before the
applications started to have problems?
Are you using the correct fiber (SM or MM)?
Did you check for a broken fiber?
Is the LED on the connected module Fibre Channel port green, and do the LEDs on any
HBA/Storage Subsystem ports indicate normal functionality?
Is there a LUN masking policy applied on the storage subsystem? If yes, is the server allowed to see
the LUNs exported by the storage array?
Is there any LUN masking policy configured on the host? Did you enable the server to see all the
LUNs it can access?
If LUN masking software is used, is the host's PWWN listed in the LUN masking database?
Is the subsystem configured for NPort?
Does the host list the subsystem's WWPN or FCID in its logs?
Does the subsystem list the host's WWPN or FCID in its logs or LUN masking database?
Can the host complete a port login (PLOGI) to the storage subsystem?
Is there any SCSI exchange that takes place between the server and the disk array?
Is the HBA configured for NPort?
Chapter 1 Troubleshooting Overview
OL-5183-02, Cisco MDS SAN-OS Release 1.3