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QFX5120-48Y 25G transceivers auto-negotiation

  • 1.  QFX5120-48Y 25G transceivers auto-negotiation

    Posted 07-29-2021 09:22
    Hi all

    Been searching through documentations but can't find the right answer


    Does anyone has idea  if

    • Is speed / duplex setting supported on 25G transceiver in QFX5120-48Y ?
    • Without any auto-negotiation configuration - is auto-negotiate enabled / disabled on 25G interface ?
    • How do we verify that ? show interface et-0/0/x extensive does not show any auto-negotiate settings

    Thank you

  • 2.  RE: QFX5120-48Y 25G transceivers auto-negotiation

    Posted 07-29-2021 10:24
    to see what auto-neg the switch knows about  try   .. I have no QFX with 10/25/50/100 so ymmv.
    show interfaces et-0/0/x media

    Autonegotiation information:
    Negotiation status: Complete
    Link partner:
    Link mode: Full-duplex, Flow control: Symmetric/Asymmetric, Remote fault: OK, Link partner Speed: 1000 Mbps
    Local resolution:
    Flow control: None, Flow control tx: None, Flow control rx: None, Remote fault: Link OK

  • 3.  RE: QFX5120-48Y 25G transceivers auto-negotiation

    Posted 07-30-2021 05:37
    Q: "Is speed / duplex setting supported on 25G transceiver in QFX5120-48?"
    A: I think 10 G and 25 G standards only have full duplex and no auto negotiation so you cannot select half and auto for that reason.

    25 G optics do require special FEC settings from time to time. set interfaces et-0/0/X ether-options fec ???

  • 4.  RE: QFX5120-48Y 25G transceivers auto-negotiation

    Posted 08-02-2021 05:28

    Can't find anything related to negotiation in the output though

    show interfaces et-0/0/31 media
    Physical interface: et-0/0/31, Enabled, Physical link is Up
      Interface index: 679, SNMP ifIndex: 555
      Link-level type: Ethernet, MTU: 9216, LAN-PHY mode, Speed: 25Gbps,
      BPDU Error: None, Loop Detect PDU Error: None, Ethernet-Switching Error: None,
      MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
      Flow control: Disabled, Media type: Fiber
      Device flags   : Present Running
      Interface flags: SNMP-Traps Internal: 0x4000
      Link flags     : None
      CoS queues     : 10 supported, 10 maximum usable queues
      Current address: 84:03:28:2e:8d:23, Hardware address: 84:03:28:2e:8d:23
      Last flapped   : 2021-07-31 16:20:30 SGT (22:55:02 ago)
      Input rate     : 4783072 bps (708 pps)
      Output rate    : 14447064 bps (827 pps)
      Active alarms  : None
      Active defects : None
      PCS statistics                      Seconds
        Bit errors                             0
        Errored blocks                         0
      Ethernet FEC Mode  :                  FEC74
      Ethernet FEC statistics              Errors
        FEC Corrected Errors                    0
        FEC Uncorrected Errors                  0
        FEC Corrected Errors Rate               0
        FEC Uncorrected Errors Rate             0
      MAC statistics:
        Input bytes: 36310827560, Input packets: 17887797,
        Output bytes: 54802385162, Output packets: 19675913
      PRBS Statistics : Disabled
      Interface transmit statistics: Disabled​

  • 5.  RE: QFX5120-48Y 25G transceivers auto-negotiation

    Posted 08-02-2021 05:28

    any idea what will happen if i were to set auto-negotiation on such interface ?
    set interface et-0/0/30 ether-options auto-negotation​​

    on the fec settings - does that means i will have to check with the host end on what fec setting do they prefer ?

    set interfaces et-0/0/30 optics-options fec ?
    Possible completions:
      hgfec                High Gain Forward Error Correction
      sdfec                Sky-Compatible Soft Decision Forward Error Correction
      sdfec15              Soft Decision Forward Error Correction with 15 percent overhead
      sdfec25              Denali-Compatible Soft Decision Forward Error Correction with 25 percent overhead​

    which option is FEC74  -- show interfaces extensive reflects that i am using FEC74 on the 25G interface

  • 6.  RE: QFX5120-48Y 25G transceivers auto-negotiation

    Posted 08-02-2021 05:47
    If the FEC is not setup the same on both ends, the link will not work at all. I had a bit of a struggle to find the cause when I had this problem the first time, so me mentioning FEC was more of a heads up for you that you might have to look for that as well if you bump into problems.

    As for auto-negotiation, I don't think it will commit or it will not matter as the setting is irrelevant for 25 G. Try it out!