1

We are running a Juniper MX480 router is a production environment. Due to increase in traffic trend , it was required to installed new FPC 'MPC-3D-16XGE-SFPP' into slot 5 of MX480. Before the addition , below was the status of 4 x FPCs installed.

user@Juniper-MX480-BB1> show chassis fpc 
                     Temp  CPU Utilization (%)   CPU Utilization (%)  Memory    Utilization (%)
Slot State            (C)  Total  Interrupt      1min   5min   15min  DRAM (MB) Heap     Buffer
  0  Online            46     24          1       23     23     23    2048       24         24
  1  Online            50     33          3       34     35     35    2048       38         39
  2  Online            47     24          0       22     22     22    2048       23         23
  3  Empty           
  4  Online            47     22          1       22     22     21    2048       26         22

However , when the FPC was installed in slot 5 chassis alarm with severity 'Major' appeared.

user@Juniper-MX480-BB1> show chassis alarms 
1 alarms currently active
Alarm time               Class  Description
2021-03-13 03:07:20 PKT  Major  CB fabric links require upgrade/training

This alarm showed for some time and then vanished.The new FPC in slot 5 also went online.

user@Juniper-MX480-BB1> show chassis fpc 
                     Temp  CPU Utilization (%)   CPU Utilization (%)  Memory    Utilization (%)
Slot State            (C)  Total  Interrupt      1min   5min   15min  DRAM (MB) Heap     Buffer
  0  Online            46     23          1       23     22     22    2048       24         24
  1  Online            50     35          3       36     35     35    2048       38         39
  2  Online            48     24          0       23     23     22    2048       23         23
  3  Empty           
  4  Online            47     22          1       25     22     22    2048       26         22
  5  Online            48     23          0       22     24     24    2048       27         21

Need to understand why this alarm appeared when Juniper MX480 supports 6 x FPCs and there is a vacant position for one more FPC in slot position 3.

Does it have something to do with 'fabric'. If so , how? We are currently running MX480 in redundant Fabric Mode.

Do we need to change the mode from redundant to increased bandwidth mode? Is it mandatory?

Since the FPC is online , what are the implications if we don't change the Fabric Mode?

user@Juniper-MX480-BB1> show chassis fabric redundancy-mode 
Fabric redundancy mode: Redundant Fabric


user@Juniper-MX480-BB1> show chassis fabric summary 
Plane   State    Uptime
 0      Online   3 days, 11 hours, 9 minutes, 19 seconds
 1      Online   3 days, 11 hours, 9 minutes, 19 seconds
 2      Online   3 days, 11 hours, 9 minutes, 12 seconds
 3      Online   3 days, 11 hours, 9 minutes, 12 seconds
 4      Spare    3 days, 11 hours, 9 minutes, 6 seconds
 5      Spare    3 days, 11 hours, 9 minutes, 5 seconds
 6      Spare    3 days, 11 hours, 8 minutes, 59 seconds
 7      Spare    3 days, 11 hours, 8 minutes, 59 seconds

Chassis Hardware

 user@Juniper-MX480-BB1> show chassis hardware clei-models 
Hardware inventory:
Item             Version  Part number  CLEI code         FRU model number
Midplane         REV 05   710-017414                     CHAS-BP-MX480-S
FPM Board        REV 02   710-017254                     CRAFT-MX480-S
PEM 0            Rev 05   740-027736                     PWR-MX480-2400-DC-S
PEM 1            Rev 05   740-027736                     PWR-MX480-2400-DC-S
PEM 2            Rev 05   740-027736                     PWR-MX480-2400-DC-S
PEM 3            Rev 05   740-027736                     PWR-MX480-2400-DC-S
Routing Engine 0 REV 07   740-031116   COUCALDBAB        RE-S-1800X4-16G-S
Routing Engine 1 REV 07   740-031116   COUCALDBAB        RE-S-1800X4-16G-S
CB 0             REV 14   750-031391   COUCARCBAA        SCBE-MX-S
CB 1             REV 15   750-031391   COUCARCBAA        SCBE-MX-S
FPC 0            REV 24   750-031088   COUIBBEBAB        MX-MPC2-3D-Q
  MIC 0          REV 26   750-028392   COUIA15BAA        MIC-3D-20GE-SFP
  MIC 1          REV 26   750-028392   COUIA15BAA        MIC-3D-20GE-SFP
FPC 1            REV 24   750-031088   COUIBBEBAB        MX-MPC2-3D-Q
  MIC 0          REV 28   750-028387   COUIA16BAA        MIC-3D-4XGE-XFP
  MIC 1          REV 26   750-028392   COUIA15BAA        MIC-3D-20GE-SFP
FPC 2            REV 26   750-031089   COUIBBDBAB        MX-MPC2-3D
  MIC 0          REV 28   750-028387   COUIA16BAA        MIC-3D-4XGE-XFP
  MIC 1          REV 31   750-028387   COUIA16BAB        MIC-3D-4XGE-XFP
FPC 4            REV 15   750-031088   COUIA18BAA        MX-MPC2-3D-Q
  MIC 1          REV 31   750-028387   COUIA16BAB        MIC-3D-4XGE-XFP
FPC 5            REV 38   750-028467                     MPC-3D-16XGE-SFPP
Fan Tray                                                 FFANTRAY-MX480-HC-S

I would be thankful if someone could explain this with details.

3
  • Can you post "show chassis hardware", I'd like to see which fabric card/FPC combination you have. – Jordan Head Mar 16 at 13:05
  • @JordanHead. Sure. I have update the question. – NABEEL NASIR Mar 16 at 17:53
  • Yep, Jeff's answer is good. – Jordan Head Mar 16 at 19:19
4

When upgrading a fabric e.g. from SCB to SCBE, there is a process to train the fabric links so they operate at higher speed. The require upgrade/training alarm is documented in the related upgrade processes (juniper doc link).

It's confusing this alarm is raised following installation of a new FPC. However, it's not anything to worry about.

I suspect this transient condition only happens with certain combinations of older line-cards and newer fabrics. The MPC-3D-16XGE-SFPP has more than its fair share of caveats!

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