Description

This article describes the issue of the Unified ISSU not being supported on the T-1600-FPC4-ES, with the revision number lower than 13. Any PIC that is running on such an FPC will go offline during ISSU. 

Symptoms

The Unified ISSU is not supported on the T-1600-FPC4-ES, with the revision number lower than 13. Any PIC that is running on such an FPC will go offline during ISSU.

Solution

The T-1600-FPC4-ES, with a revision number lower than 13, uses SL-chip 2.0. This version of SL-chip does not support ISSU and will cause the FPC to reset.

SL-chip 2.1 supports ISSU, which is installed on the FPC with revision 13 and higher. You can check the hardware revision number of the FPC with the show chassis hardware command. In the following example, FPC 0 is REV 06 and older than REV 13 : 

user@t1600> show chassis hardware detail
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                                  T1600
~snip~
FPC 0            REV 06   710-013037                     FPC Type 4-ES
  CPU            REV 05   710-016744                     ST-PMB2
  PIC 0          REV 11   750-017405                     4x 10GE (LAN/WAN) XFP
    Xcvr 1       REV 02   740-014289                     XFP-10G-SR
    Xcvr 2       REV 02   740-014289                     XFP-10G-SR
  PIC 1          REV 11   750-017405                     4x 10GE (LAN/WAN) XFP
    Xcvr 0       REV 02   740-014289                     XFP-10G-SR
    Xcvr 1       REV 01   740-014289                     XFP-10G-SR
  MMB 0          REV 04   710-016036                     ST-MMB2
  MMB 1          REV 04   710-016036                     ST-MMB2
You can check the version of the SL-chip with a CLI command; you do not need to access the FPC. Use the following command to check the version of SL-chip: 
> request pfe execute target fpc0 command "show lchip"
SENT: Ukern command: show lchip
GOT:
GOT: SL-chip global information:
GOT:
GOT: SLCHIP 0: Initialized
GOT: Version 2, Minor ID 0, PIC Slot(s) 0.
GOT: STREAM 0 has 1 IFDs.
GOT: STREAM 16 has 1 IFDs.
GOT: STREAM 32 has 1 IFDs.
GOT: STREAM 48 has 1 IFDs.
GOT:
GOT: SLCHIP 1: Initialized
GOT: Version 2, Minor ID 0, PIC Slot(s) 1.
GOT: STREAM 0 has 1 IFDs.
GOT: STREAM 16 has 1 IFDs.
GOT: STREAM 32 has 1 IFDs.
GOT: STREAM 48 has 1 IFDs.
GOT:
GOT: SLCHIP 2: Not Initialized
GOT:
GOT: SLCHIP 3: Not Initialized
GOT:
LOCAL: End of file

Correction Notes:

Regarding the new T-1600-FPC4-ES, even with a revision number lower than 13, it might use SL-chip 2.1 which supports ISSU. Take the one with part number 710-033871, for example:  

> show chassis hardware models | grep T1600-FPC4-ES  
FPC 0            REV 03   710-033871   BBAH8636          T1600-FPC4-ES
FPC 1            REV 06   710-033871   CACD6424          T1600-FPC4-ES
FPC 2            REV 04   710-033871   BBAP4943          T1600-FPC4-ES
FPC 3            REV 04   710-033871   BBAP3676          T1600-FPC4-ES
FPC 4            REV 05   710-033871   BBAV0079          T1600-FPC4-ES
FPC 5            REV 03   710-033871   BBAJ0846          T1600-FPC4-ES

> request pfe execute target fpc0 command "show lchip"    
SENT: Ukern command: show lchip
GOT:
GOT: SL-chip global information:
GOT:
GOT: SLCHIP 0:  Initialized
GOT:            Version 2, Minor ID 1, PIC Slot(s) 0.
GOT:  STREAM  0 has 1 IFDs.
GOT:  STREAM 16 has 1 IFDs.
GOT:  STREAM 32 has 1 IFDs.
GOT:  STREAM 48 has 1 IFDs.
GOT:
GOT: SLCHIP 1:  Initialized
GOT:            Version 2, Minor ID 1, PIC Slot(s) 1.
GOT:  STREAM  0 has 1 IFDs.
GOT:  STREAM 16 has 1 IFDs.
GOT:  STREAM 32 has 1 IFDs.
GOT:  STREAM 48 has 1 IFDs.
GOT:
GOT: SLCHIP 2:  Not Initialized
GOT:
GOT: SLCHIP 3:  Not Initialized
GOT:
LOCAL: End of file

To sum up: We should check the SL-chip version instead of the T-1600-FPC4-ES revision for ISSU supportability. When the SL-chip version is 2.1 or above, that means this T-1600-FPC4-ES  supports ISSU, and vice versa.