Connectrix: MDS switch with CFS ipv4/ipv6 enabled reloads unexpectedly

In rare circumstances, an MDS fabric switch may unexpectedly reload. In certain situations, the switch may then enter into a continuous boot loop (see Further Problem Description for recovery steps in this case).

The reason for the reload is Kernel Panic.

`show system reset-reason`
----- reset reason for module 1 (from Supervisor in slot 1) ---
1) At 875120 usecs after Wed Sep 23 11:29:06 2020
Reason: Kernel Panic
Service:
Version: 8.4(1a)

This issue may happen only in the following circumstances:    

• Switch model is one of the following:      

• CFS distribution over ipv4 or ipv6 is configured on the switch:     

By far, the most common use case for CFS distribution over ipv4/ipv6 is NPV mode, as in that configuration CFS distribution over FC is not supported. Since NPV mode is not supported on MDS 9250i, this software defect is less likely to occur on this, than on the other two affected platforms. One topology where it could still be implicated would be an MDS 9250i as core switch with one or more NPV switches downstream.

Resolution:     
Upgrade to NX-OS 8.4.2a

Workaround:     

1. If the affected device is running in NPV mode, disable CFS distribution completely.

2. If the affected device is running in switch mode, disable CFS distribution over ipv4/ipv6.