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Cisco Bug: CSCsz30515 - SUP720 crash due to tsptun_frr_process process hang

Last Modified

Jan 24, 2017

Products (1)

  • Cisco IOS

Known Affected Releases

12.2(18)

Description (partial)

Symptom:  
 customer running 12.2(18)SXF14 and later special image including 12.2(18)SXF16
 has observed SUP720 crashes with following messages
  
 %CPU_MONITOR-SP-6-NOT_HEARD: CPU_MONITOR messages have not been heard for 31
seconds [6/1]
 Apr 24 15:54:20.295 UTC: %CPU_MONITOR-SP-6-NOT_HEARD: CPU_MONITOR messages 
have not been heard for   61 seconds [6/1]
 Apr 24 15:54:48.627 UTC: %CPU_MONITOR-SP-6-NOT_HEARD: CPU_MONITOR messages 
have not been heard for   90 seconds [6/1]
 Apr 24 15:55:14.955 UTC: SP: icc_send_request_internal: ipc_send_rpc_blocked
failed, result 6
 Apr 24 15:55:14.959 UTC: SP: -Traceback= 404F5BF0 404F5DA8 404F6028 403AC090
403AC7DC

The failure to respond to CPU_MONITOR messages occurs because the RP does not respond to heartbeats because it is stuck here:

%SYS-2-INTSCHED: 'idle' at level 2
-Process= "LSP Tunnel FRR", ipl= 2, pid= 161
-Traceback= 41D7FCA0 41069610 42141640
%SYS-2-INTSCHED: 'idle' at level 2
-Process= "LSP Tunnel FRR", ipl= 2, pid= 161
-Traceback= 41D7FCA0 41069610 42141640

Conditions: The crashes occur during configuration activities on heavily loaded routers
 but there is no clear triggering condition, neither a sequence of commands nor a network event. 
 Neither we nor the customer can reproduce the issue in a lab situation.   

The "LSP_Tunnel FRR" process handles LSPs (Label Switched Paths) configured for FRR (Fast 
ReRoute) using MPLS Traffic-Engineering.  The affected router and the other routers in this network are not configured to run MPLS Traffic-Engineering, nor Fast ReRoute.  

This fix (CSCsz30515) prevents the "LSP Tunnel FRR" process from running unless an interface protected by FRR experiences a "DOWN" event and constitutes an optimization of the Cisco IOS software. 

The underlying cause of this problem ("LSP Tunnel FRR" process stuck, resulting in reload) was determined to be CSCek68108.
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