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FPC reconnects when graceful RE switchover is performed

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Article ID: KB33269 KB Last Updated: 02 Nov 2018Version: 1.0
Summary:

This article discusses how FPCs reconnect when a graceful RE switch over is performed on an M120 device.

Symptoms:

In a dual RE scenario when RE switchover occurs either gracefully or ungracefully, the following may be observed:

Consider an M120 device with dual REs and empty FPC slots:

lab@M120-R1# run show chassis routing-engine | no-more
Oct 19 10:59:59
Routing Engine status:
  Slot 0:
    Current state                  Backup
    Election priority              Master (default)
    Temperature                 44 degrees C / 111 degrees F
    CPU temperature             45 degrees C / 113 degrees F
    DRAM                      2048 MB (2048 MB installed)
    Memory utilization          24 percent
    CPU utilization:
      User                       0 percent
      Background                 0 percent
      Kernel                     1 percent
      Interrupt                  0 percent
      Idle                      99 percent
    Model                          RE-A-2000
    Serial ID                      1000737665
    Start time                     2018-10-15 10:49:34 IST
    Uptime                         4 days, 10 minutes, 7 seconds
    Last reboot reason             0x11:power cycle/failure misc hardware reason
    Load averages:                 1 minute   5 minute  15 minute
                                       0.00       0.00       0.00
Routing Engine status:
  Slot 1:
    Current state                  Master
    Election priority              Backup (default)
    Temperature                 44 degrees C / 111 degrees F
    CPU temperature             48 degrees C / 118 degrees F
    DRAM                      2048 MB (2048 MB installed)
    Memory utilization          29 percent
    CPU utilization:
      User                       0 percent
      Background                 0 percent
      Kernel                     7 percent
      Interrupt                  0 percent
      Idle                      93 percent
    Model                          RE-A-2000
    Serial ID                      9012002390
    Start time                     2018-10-15 10:37:36 IST
    Uptime                         4 days, 22 minutes, 20 seconds
    Last reboot reason             Router rebooted after a normal shutdown.
    Load averages:                 1 minute   5 minute  15 minute
                                       0.11       0.09       0.04
 
 
[MASTER]
lab@M120-R1> show chassis fpc
Oct 19 11:02:05
                     Temp  CPU Utilization (%)   Memory    Utilization (%)
Slot State            (C)  Total  Interrupt      DRAM (MB) Heap     Buffer
  0  Online            50      0          0       128         7         51
  1  Online            43      0          0       128         7         51
  2  Online            35      0          0       128         9         51
  3  Empty          
  4  Online            30      0          0       128        11         51
  5  Empty          
 

When RE switchover occurs, the following may be observed:

[MASTER]
lab@M120-R1> request chassis routing-engine master switch
Oct 19 11:03:20
Toggle mastership between routing engines ? [yes,no] (no) yes
Oct 19 11:03:26
 
Resolving mastership...
Complete. The other routing engine becomes the master.
 
[BACKUP]
lab@M120-R1>
 
Oct 19 11:03:48 CHASSISD_FRU_OFFLINE_NOTICE: Taking FPC 3 offline: FRU did not reconnect
Oct 19 11:03:48  fpc_down slot 3 reason Removal cargs 0x0
Oct 19 11:03:48  fpc_offline_now - slot 3, reason: FRU did not reconnect, error OK transition state 1
Oct 19 11:03:48  send: red alarm set, device FPC 4, reason FEB not online for FPC 4
Oct 19 11:03:48 CHASSISD_FRU_OFFLINE_NOTICE: Taking FPC 5 offline: FRU did not reconnect
Oct 19 11:03:48  fpc_down slot 5 reason Removal cargs 0x0
Oct 19 11:03:48  fpc_offline_now - slot 5, reason: FRU did not reconnect, error OK transition state 1

 

Solution:

When RE switchover occurs with GRES enabled, the chassisd attempts to do a soft reconnect on all the slots of the chassis regardless of whether or not an FPC is present. The above messages indicate that due to slot 3 and slot 5 being empty, there was no reconnect. Hence, the respective FPC slots were taken offline.

The slots that have FPCs will be able to successfully establish a soft reconnect and will operate normally without any impact as observed below:

Oct 19 11:03:26  FPC 0 added
Oct 19 11:03:26  reading FPC 0 initial state
Oct 19 11:03:26  check_and_carp_on_i2cs_version I2CS version=0xf
Oct 19 11:03:27  Done reading FPC 0 initial state
Oct 19 11:03:27  FPC 1 added
Oct 19 11:03:27  reading FPC 1 initial state
Oct 19 11:03:27  check_and_carp_on_i2cs_version I2CS version=0xf
Oct 19 11:03:28  Done reading FPC 1 initial state
Oct 19 11:03:28  FPC 2 added
Oct 19 11:03:28  reading FPC 2 initial state
Oct 19 11:03:28  check_and_carp_on_i2cs_version I2CS version=0xf
Oct 19 11:03:29  Done reading FPC 2 initial state
Oct 19 11:03:29  FPC 4 added
Oct 19 11:03:29  reading FPC 4 initial state
Oct 19 11:03:30  check_and_carp_on_i2cs_version I2CS version=0xf
Oct 19 11:03:30  Done reading FPC 4 initial state

It can also be noted from the uptime of the FPCs that the FPCs did not restart and only went through a soft restart with the chassisd process of the current master RE.

lab@M120-R1> show chassis fpc detail
Oct 19 11:38:07
Slot 0 information:
  State                               Online   
  Temperature                      50 degrees C / 122 degrees F
  Total CPU DRAM                  128 MB
  Start time                          2018-10-15 10:10:41 IST
  Uptime                              4 days, 1 hour, 27 minutes, 26 seconds
Slot 1 information:
  State                               Online   
  Temperature                      43 degrees C / 109 degrees F
  Total CPU DRAM                  128 MB
  Start time                          2018-10-15 10:10:43 IST
  Uptime                              4 days, 1 hour, 27 minutes, 24 seconds
Slot 2 information:
  State                               Online   
  Temperature                      35 degrees C / 95 degrees F
  Total CPU DRAM                  128 MB
  Start time                          2018-10-15 10:10:46 IST
  Uptime                              4 days, 1 hour, 27 minutes, 21 seconds
Slot 4 information:
  State                               Online   
  Temperature                      31 degrees C / 87 degrees F
  Total CPU DRAM                  128 MB
  Start time                          2018-10-15 10:10:54 IST
  Uptime                              4 days, 1 hour, 27 minutes, 13 seconds
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