constant FEC errors juniper mpc10e 400g

Wed Apr 17 19:36:39 UTC 2024

We recently added MPC10E-15C-MRATE cards to our MX960's to upgrade our core to 400g.  During initial testing of the 400g interface (400GBASE-FR4), I see constant FEC errors.  FEC is new to me.  Anyone know why this is occurring?  Shown below, is an interface with no traffic, but seeing constant FEC errors.  This is (2) MX960's cabled directly, no dwdm or anything between them... just a fiber patch cable.

{master}
me at mx960> clear interfaces statistics et-7/1/4

{master}
me at mx960> show interfaces et-7/1/4 | grep rror | refresh 2
---(refreshed at 2024-04-17 14:18:53 CDT)---
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC statistics              Errors
     FEC Corrected Errors                    0
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate               0
     FEC Uncorrected Errors Rate             0
---(refreshed at 2024-04-17 14:18:55 CDT)---
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC statistics              Errors
     FEC Corrected Errors                 4302
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate               8
     FEC Uncorrected Errors Rate             0
---(refreshed at 2024-04-17 14:18:57 CDT)---
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC statistics              Errors
     FEC Corrected Errors                 8796
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate             146
     FEC Uncorrected Errors Rate             0
---(refreshed at 2024-04-17 14:18:59 CDT)---
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC statistics              Errors
     FEC Corrected Errors                15582
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate             111
     FEC Uncorrected Errors Rate             0
---(refreshed at 2024-04-17 14:19:01 CDT)---
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC statistics              Errors
     FEC Corrected Errors                20342
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate             256
     FEC Uncorrected Errors Rate             0

{master}
me at mx960> show interfaces et-7/1/4 | grep "put rate"
   Input rate     : 0 bps (0 pps)
   Output rate    : 0 bps (0 pps)

{master}
me at mx960> show interfaces et-7/1/4
Physical interface: et-7/1/4, Enabled, Physical link is Up
   Interface index: 226, SNMP ifIndex: 800
   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
   Flow control: Enabled
   Pad to minimum frame size: Disabled
   Device flags   : Present Running
   Interface flags: SNMP-Traps Internal: 0x4000
   Link flags     : None
   CoS queues     : 8 supported, 8 maximum usable queues
   Schedulers     : 0
   Last flapped   : 2024-04-17 13:55:28 CDT (00:36:19 ago)
   Input rate     : 0 bps (0 pps)
   Output rate    : 0 bps (0 pps)
   Active alarms  : None
   Active defects : None
   PCS statistics                      Seconds
     Bit errors                             0
     Errored blocks                         0
   Ethernet FEC Mode  :                 FEC119
   Ethernet FEC statistics              Errors
     FEC Corrected Errors               801787
     FEC Uncorrected Errors                  0
     FEC Corrected Errors Rate            2054
     FEC Uncorrected Errors Rate             0
   Link Degrade :
     Link Monitoring                   :  Disable
   Interface transmit statistics: Disabled

   Logical interface et-7/1/4.0 (Index 420) (SNMP ifIndex 815)
     Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
     Input packets : 1
     Output packets: 1
     Protocol inet, MTU: 1500
     Max nh cache: 75000, New hold nh limit: 75000, Curr nh cnt: 1, Curr new hold cnt: 0, NH drop cnt: 0
       Flags: Sendbcast-pkt-to-re
       Addresses, Flags: Is-Preferred Is-Primary
         Destination: 10.10.10.76/30, Local: 10.10.10.77, Broadcast: 10.10.10.79

-- 
-Aaron
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