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7600 Minor Error due to TestErrorCounterMonitor

Adrian Jimenez
Cisco Employee
Cisco Employee

Hello Community, 

 

Lately I dealt with an issue on a 7600 Chassis and a minor error on  a module. The normal troubleshooting suggested for a minor error is reseat the line card and if it wipes the error it was a transient issue and if the issue stands this indicates a hardware failure on the module. Next time you are troubleshooting for minor errors make sure you investigate what is the online diagnostic that the switch is running and that is not passing, with this we can confirm if in fact there is a hardware failure or something more complex and deeper, such as TestErrorCounterMonitor diagnostic is this scenario. 

 

This output can be pulled from the "show diagnostic events" when a minor/major error event is experienced. 

 

The minor error was caused because the module was passing traffic across a MPLS cloud, the error was caused by some failed lookups due to the need for an extra lookup to process the labels or traffic.  Basically the lookup requires two cycles through the forwarding engine before it can be forwarded out the interface configured for MPLS.  After one lookup, if the complete set of lookups is not completed, it will cause the error on the module.

 

In order to overcome this issue we applied the "mls mpls recir-agg" (global command) to the PE MPLS routers, which will be an aggregate that in the end with be a summary route or per vrf label for MPLS. Per prefix label is the normal behavior where a label is generated per prefix in a vrf rather than a per vrf label.

 

The impact of the minor error should be minimal as it is only the traffic that is not complete after one lookup that is recirculated for a second pass, but could affect somehow the forwarding of the packets, all other traffic is handled in one pass as normal.

 

With the workaround explained above the issue experienced was fixed and the traffic passing across module was restored and in good conditions. Just keep in mind this scenario when dealing with a Minor Error on a module passing traffic over MPLS. 

 

Hope this helps sometime! 

 

Adrian Jimenez 

 

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