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Cisco Bug: CSCvt85747 - Multiple interrupted show techs may lead to process hangs and system restart on an NCS5500

Last Modified

Sep 16, 2020

Products (14)

  • Cisco Network Convergence System 5500 Series
  • Cisco Network Convergence System 55A2-MOD-HD-S
  • Cisco Network Convergence System 5504
  • Cisco Network Convergence System 5516
  • Cisco Network Convergence System 5502-SE
  • Cisco Network Convergence System 5508
  • Cisco Network Convergence System 5502
  • Cisco IOS XR Software
  • Cisco Network Convergence System 55A1-24H
  • Cisco Network Convergence System 55A2-MOD-S
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Known Affected Releases

6.6.25

Description (partial)

Symptom:
When show tech is collected continuously through a script and the script aborts due to a time out, leads to SSH sessions created during show tech collection not being cleaned up. Over time, after more than 250 days of runtime, below number of SSH sessions are present on the system : 

RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sshd | u wc -l
296
RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sftp | u wc -l
295

This leads to NCS5500 being restarted, as the maximum resource limit is reached.


After NCS5500 restart:

RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sshd | u wc -l
5
RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sftp | u wc -l
2

When the script aborts, vty telnet session is interrupted while collecting show techs, leading to stale SSH sessions to increase:

RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sshd | u wc -l
6
RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sftp | u wc -l
5
RP/0/RP0/CPU0:NCS-55A1-A#! script vty session interrupted while collecting show tech
RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sshd | u wc -l
7
RP/0/RP0/CPU0:NCS-55A1-A#show process memory location 0/RP0/CPU0 | i sftp | u wc -l
6

Conditions:
Several collections (more than 250) of show tech where the vty telnet session to the system is interrupted  before show tech collection finishes.
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Bug Details Include

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