MDS fabric switch with cfs ipv4/ipv6 enabled reloads unexpectedly

Notification

Risk classification

Informational

Risk categories

System Outage

Subcategories for Informational notifications

Troubleshooting & Fixes

Affected Domain

Cisco MDS switch models 9396S (9711-S96), 9148S (9711-S48) or 9250i (8977-R50, 9710-E01) running NX-OS version 8.4(1), 8.4(1a) or 8.4(2.214).

Abstract

Affected switch models running a specified NX-OS version may experience an unexpected reload of the fabric in rare circumstances, and could subsequently enter into a continuous boot loop.

Description

The problem can occur only if CFS distribution over ipv4 or ipv6 is configured on the switch:

cfs ipv4 distribute
cfs ipv6 distribute

The most common use of CFS distribution is NPV mode. Because NPV is not supported in 9250i, the problem is less likely to occur on this model.

A full explanation of the problem, defect CSCvs87512, can be found here in Cisco's Bug Search Tool.

Recommended Action

The defect is fixed in NX-OS versions 8.4(2a) and 8.4(2b). Upgrading to one of these versions will resolve the problem.

If you cannot upgrade, a workaround is to disable cfs distribution. If the affected device is running in NPV mode:

     config t
     no cfs distribute
     no cfs ipv4 distribute
     no cfs ipv6 distribute

If the affected device is running in switch mode, disable cfs distribution over ipv4/ipv6:

     config t
     no cfs ipv4 distribute
     no cfs ipv6 distribute

In case the switch enters into a boot loop, perform the following steps to recover:

Connect the serial console.
Disable mgmt0 interface on the switch, either by unplugging the cable, or by shutting down the port on the peer ethernet switch.
Power cycle the switch -- boot loop should stop.
Perform the workaround, as per steps above.
Bring the mgmt0 interface back up.

In case the serial console connectivity is not available, please contact IBM support for further assistance.

Reference ID

Cisco defect CSCvs87512

Date first published

03 December 2020

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