• Downgrading directly from Cisco MDS NX-OS Release 9.4(2a) to Cisco MDS NX-OS Release 9.4(2) is not recommended.

• Downgrading directly from Cisco MDS NX-OS Release 9.x to unsupported releases are disruptive.

• Downgrading directly from Cisco MDS NX-OS Release 9.x to releases before Cisco MDS NX-OS Release 6.2(9) is not supported. In such a scenario, we recommend that you first downgrade to Cisco MDS NX-OS Release 6.2(13a) or higher and then downgrade to the required release.

• Downgrading directly from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(0)DY(1) is not supported. In such a scenario, we recommend that you first downgrade to Cisco MDS NX-OS Release 7.3(0)D1(1) and then upgrade to 7.3(0)DY(1).

• Downgrading directly from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(1)DY(1) is not supported. In such a scenario, we recommend that you first downgrade to Cisco MDS NX-OS Release 7.3(0)D1(1) and then upgrade to 7.3(1)DY(1).

• Downgrading from Cisco MDS NX-OS Release 9.x is not supported if the FLOGI Scale Optimization feature is enabled on Cisco MDS 9718 Switches.

• We do not recommend parallel In-Service Software Downgrade (ISSD) on Cisco MDS 9148S, Cisco MDS 9250i, and Cisco MDS 9396S fabric switches when these fabric switches are each other’s peers.

• If you are downgrading from Cisco MDS NX-OS Release 9.x to a release prior to Cisco MDS NX-OS Release 9.2(1), ensure that you use the clear logging onboard txwait command after downgrading. Otherwise, logging to the OBFL TxWait file may cease with an error. For more information, see the Cisco MDS 9000 Series Interfaces Configuration Guide, Release 9.x.

• If you copy firmware using the SFTP or SCP clients after enabling the feature scp-server or feature sftp-server command on your switch, ensure that you close the SFTP or SCP connection using the no feature scp-server or no feature sftp-server command before performing ISSD. Otherwise, ISSD will be disruptive. To avoid this issue, we recommend that you transfer files to the switch using the copy command instead or using the DCNM client.

• Prior to upgrade or downgrade, reset the switch's logging levels to the system defaults via the no logging level all configuration command. If this is not done, the upgrade or downgrade may be disruptive due to excessive logging causing control plane downtime exceeding 80 seconds.

  Before entering the no logging level all command, ensure that the switch's current logging configuration is saved. This will need to restored after the upgrade or downgrade.

  Follow these steps:

  1. Enter the show running-config | i “logging level” command and save the output. These are the switch's current settings.

  2. Enter the no logging level all command in configuration mode.

  3. Perform upgrade or downgrade.

  4. Restore logging level configuration using the output that was saved from Step 1.

• To determine if high-bandwidth capability is enabled, use the show hardware fabric-mode command. The following example shows that the higher bandwidth capability is not activated:

  switch# show hardware fabric-mode
  Fabric mode supports only one configuration of 8G FC modules - 4/44 Host-Optimized 8G FC module.
  switch# 

  The following example shows that the higher bandwidth capability is activated:

  switch# show hardware fabric-mode
  fabric mode supports FCoE, Gen2 and above linecards
  switch# 

For information on supported chassis and modules, see the Cisco MDS 9000 Series Compatibility Matrix. For information on the procedures for installing and upgrading software for Intelligent Storage Services on the Cisco MDS 9000 Series Storage Services Module (SSM), see the Cisco MDS 9000 Series Storage Services Module Software Installation and Upgrade Guide.

• Downgrading from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(0)D1(1) or Cisco MDS NX-OS Release 6.2(13a) is not supported on a Cisco MDS 9396S Switch which has DS-CAC-1200W as a power supply unit (PSU) and DS-C96S-FAN-I as port side intake fan tray.

• Downgrading from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 6.2(13) is not supported on the Cisco MDS 9396S Multilayer Fabric Switch. The minimum recommended image for Cisco MDS 9396S Multilayer Fabric Switch is 6.2(13a).

• To downgrade from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(x) on a Cisco MDS 9396S Series switch, you must first disable the extended receive BB_credit configuration using the no feature fcrxbbcredit extended command. After the downgrade process is complete, enable the extended receive BB_credit configuration using the feature fcrxbbcredit extended command.

• Downgrading from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(0)D1(1), or 6.2(13a) and lower is not supported on a Cisco MDS 9250i Switch which has only one online PSU.

• Downgrading from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(0)D1(1), or 6.2(13a) and lower on a Cisco MDS 9250i Switch with two online PSUs results in loss of N:N grid redundancy. The switch will run in non-redundant mode.

• Downgrading from Cisco MDS NX-OS Release 9.x to Cisco MDS NX-OS Release 7.3(0)D1(1), or 6.2(13a) and lower on a Cisco MDS 9250i Switch with three online PSUs results in loss of N:N grid redundancy. The switch will run in N+1 power redundant mode.