Not to belabor this, but so interesting... I need a FEC-for-Dummies or FEC-for-IP/Ethernet-Engineers...

Shown below, my 400g interface with NO config at all... Interface has no traffic at all, no packets at all....  BUT, lots of FEC hits.  Interesting this FEC-thing.  I'd love to have a fiber splitter and see if wireshark could read it and show me what FEC looks like...but something tells me i would need a 400g sniffer to read it, lol

It's like FEC (fec119 in this case) is this automatic thing running between interfaces (hardware i guess), with no protocols and nothing needed at all in order to function.

-Aaron

{master}
me@mx960> show configuration interfaces et-7/1/4 | display set

{master}
me@mx960>

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

{master}
me@mx960> show interfaces et-7/1/4 | grep packet
    Input packets : 0
    Output packets: 0

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

{master}
me@mx960> show interfaces et-7/1/4 | grep rror
  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                28209
    FEC Uncorrected Errors                  0
    FEC Corrected Errors Rate            2347
    FEC Uncorrected Errors Rate             0

{master}
me@mx960> show interfaces et-7/1/4 | grep packet
    Input packets : 0
    Output packets: 0

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

{master}
me@mx960> show interfaces et-7/1/4 | grep rror
  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                45153
    FEC Uncorrected Errors                  0
    FEC Corrected Errors Rate              29
    FEC Uncorrected Errors Rate             0

{master}
me@mx960> show interfaces et-7/1/4 | grep packet
    Input packets : 0
    Output packets: 0

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

{master}
me@mx960> show interfaces et-7/1/4 | grep rror
  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                57339
    FEC Uncorrected Errors                  0
    FEC Corrected Errors Rate            2378
    FEC Uncorrected Errors Rate             0

{master}
me@mx960>

On 4/18/2024 7:13 AM, Mark Tinka wrote:

On 4/17/24 23:24, Aaron Gould wrote:

Well JTAC just said that it seems ok, and that 400g is going to show 4x more than 100g "This is due to having to synchronize much more to support higher data."

We've seen the same between Juniper and Arista boxes in the same rack running at 100G, despite cleaning fibres, swapping optics, moving ports, moving line cards, e.t.c. TAC said it's a non-issue, and to be expected, and shared the same KB's.

It's a bit disconcerting when you plot the data on your NMS, but it's not material.

Mark.

-- 
-Aaron