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Cisco Bug: CSCum48824 - N3K: Downgrade Fails PFC int. Incompatibility Check after Show Start CMD

Last Modified

Feb 15, 2018

Products (1)

  • Cisco Nexus 3000 Series Switches

Known Affected Releases

6.0(2)U2(2Z)

Description (partial)

Symptom:
Downgrade using install all from a 6.0.2.U2 image to 5.0.3.Ux based image will fail with the following warning

"Running-config contains configuration that is incompatible with the new image (strict incompatibility). 
 Please run 'show incompatibility system <image>' command to find out which feature needs to be disabled.".
[#                   ]   0% -- FAIL. Return code 0x40930029 (Current running-config is not supported by new image).
Pre-upgrade check failed. Return code 0x40930029 (Current running-config is not supported by new image).

Checking incompatibility will show that PFC is still enabled even when all interfaces have PFC disabled (mode auto)

Test-Host-Name# show incompatibility system n3000-uk9.5.0.3.U5.1f.bin
The following configurations on active are incompatible with  the system image  
1) Service : ipqosmgr , Capability : CAP_FEATURE_N3K_IPQOS_DCE_PFC_CFG 
Description : Non default priority-flow-control configured. 
Capability requirement : STRICT 
Disable command : Use "show interface priority-flow-control" to find which interfaces have non-default configuration. Set these interfaces to default (auto mode) using the command "priority-flow-control mode auto"

Conditions:
This happens only under the following conditions

 a) PFC is configured and at least one interface has PFC enabled (mode on or mode off)
 b) After PFC is configured and enabled, the device is reloaded or 'copy run start' is done. Then 'show start' command is issued
 c) PFC configuration is removed
 d) After removing PFC configuration, image downgrade is attempted using "install all" CLI
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