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EX-4200 switch port showing Half Duplex

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  • 1.  EX-4200 switch port showing Half Duplex

    Posted 07-11-2018 07:50

    I was wondering if anyone else was showing the same output when checking interface status. After our most recent upgrade to 15.1R7.8 our interfaces have been showing (Speed: Auto, Duplex: Half-duplex) instead of (Speed: Auto, Duplex: Auto) as in other versions. The Link partner shows connected at Link mode: Full-duplex, Speed: 1000 Mbps. I'm not sure if it's causing problems, but as I look through the statistics I think it is. This port currently has 9591 drops. I just cleared the stats and will monitor. We're showing the same behavior across many other virtual chassis and stand alone chassis. If this is a duplicate forum post my apologies in advance.
    > show interfaces ge-0/0/16 media
    Physical interface: ge-0/0/16, Enabled, Physical link is Up
      Interface index: 340, SNMP ifIndex: 1229
      Link-level type: Ethernet, MTU: 1514, LAN-PHY mode, Speed: Auto, Duplex: Half-duplex, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled, Auto-negotiation: Enabled,
      Remote fault: Online, Media type: Copper
      Device flags   : Present Running
      Interface flags: SNMP-Traps Internal: 0x0
      Link flags     : None
      CoS queues     : 8 supported, 8 maximum usable queues
      Current address: xx:xx:xx:xx:xx:xx, Hardware address: xx:xx:xx:xx:xx:xx
      Last flapped   : 2018-07-10 18:01:17 EDT (16:28:43 ago)
      Input rate     : 512 bps (1 pps)
      Output rate    : 2096 bps (3 pps)
      Active alarms  : None
      Active defects : None
      MAC statistics:
        Input bytes: 61117235598, Input packets: 104139384, Output bytes: 44274883406, Output packets: 116256253
      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: Symmetric, Remote fault: Link OK
      Interface transmit statistics: Disabled
    > show configuration interfaces ge-0/0/16
    unit 0 {
        family ethernet-switching {
            vlan {
                members WORKSTATIONS;
    Model: ex4200-48t
    Junos: 15.1R7.8

  • 2.  RE: EX-4200 switch port showing Half Duplex
    Best Answer

    Posted 07-11-2018 15:09

    Saw the same issue on the QFX/ACX platform and it was just a cosmetic incorrect showing in the interface but I don't see the ex listed in the PR.  This was fixed in Junos 17




  • 3.  RE: EX-4200 switch port showing Half Duplex

    Posted 07-12-2018 05:35

    Thanks for the reply and the PR link. I think it's cosmetic in the EX case also. There hasn't been any collisions or drops in the 21 hours since the statistics were last cleared.

  • 4.  RE: EX-4200 switch port showing Half Duplex

    Posted 07-11-2018 15:15

    What is the actual link partner and how is it configured?  Looks like link partner may auto-neg speed only, which would cause EX4200 port set to auto to default to half-duplex.

  • 5.  RE: EX-4200 switch port showing Half Duplex

    Posted 07-12-2018 05:37

    rccpgm - It's a mix of servers and workstations all configured for Auto Speed / Auto Duplex.

  • 6.  RE: EX-4200 switch port showing Half Duplex

    Posted 07-12-2018 06:13

    FYI, EX4200 can never run 17.x code.  EX4200 code support stops at 15.1R'x'.  @LovingTheJunos, if you plug a PC set for Auto into a port on the EX4200, what does the EX4200 show?  This could be a cosmetic bug in 15.1R7.  What code release were you running previously?

  • 7.  RE: EX-4200 switch port showing Half Duplex

    Posted 07-12-2018 13:15

    @rccpgm Thanks for the FYI...prior to running 15.1R7 we were at  version 15.1R6.7. The command output in the original post was of a port with a PC set for Auto/Auto.

  • 8.  RE: EX-4200 switch port showing Half Duplex

    Posted 04-13-2019 13:55

    Hello all,


    This is known issue on this code and the correction is on code 15.1R7-S2.

    There is a PR about it, please check below:



    Hope it helps!