Why Zyxel XS1920 doesn't work with file writes from a PC to a QNAP NAS?

If I connect AORUS Xtreme x540 with 10gbase-t through Zyxel XS1920 then to QNAP TVS-872xt with 10gbase-t, with 9000 jumbo frames enabled in Windows 10 and QNAP side. Writing a file of cca 200MB size renders my Windows 10 PC to not been able to reach the mounted drive, unless I reboot my Windows PC. Also AJA System Test fails to write to the mounted drive.

If I take out the Zyxel XS1920 and just directly connect the PC to QNAP with 10gbase-t, then it works without any problem, including good transfer speed is reached.

if I ping with
  ping -f -l 8972 ip_address_of_qnap
it works, but I cannot send larger packets than 8972. It says ''Packet needs to be fragmented but DF set."
With or without Zyxel XS1920, this jumbo packet ping works in the same way.

Anybody have some ideas how to investigate the cause of this annoying thing? How can I use QNAP through XS1920? Is there something special to be set?

All Replies

  • Kim
    Kim Posts: 37  Freshman Member
    Is it possible that the issue is related to your PC? Based on your description, your PC is not able to reach the mounted drive unless you reboot PC. If the issue is related to switch, I think rebooting PC will not fix the issue.
  • TiggerLAS
    TiggerLAS Posts: 64  Ally Member
    First Anniversary First Answer First Comment

    If you haven't done so already, log into your switch,
    and navigate to your interface settings for your VLANS.

    The XS1920, may, by default, have an MTU size of 1500 set.

    Note that if you are running different VLANS, that there may be
    separate VLAN settings for each interface (not port) defined.

    If you're not sure where the settings are located,
    you should be able to search "MTU" in the user manual.

    If your MTU is already at 9000, then I'm not sure.

    You can certainly use PING to determine what MTU
    the switch seems to be passing, in order to confirm this.

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