Does anybody know, or has anybody worked with Korenix JetNet 4508v2? This Switch has a very important Bug in the Firmware. SSH is working fine, but for a period of time. Then, ssh is not working anymore, and unfortunately you dont have direct access to the switch. I am working remotely, and i have to call the Colleague there to restart the Switches. Can anyone suggest any solution to this issue? Thanks in advance.

  • 1
    If, as you claim, it is a firmware bug, you need to upgrade the firmware.
    – Ron Maupin
    Sep 10, 2019 at 14:18
  • Depending on what the bug is, preemtively restarting the SSH daemon before it stops working may help (but may also introduce new problems), or connecting the device to a serial console server so you have another way to access it may work. But as Ron said, getting a firmware upgrade sounds like the best thing to do.
    – Teun Vink
    Sep 10, 2019 at 14:25
  • @RonMaupin, I have upgraded the latest Firmware, but there is nothing to fix this issue.
    – Jim Pap
    Sep 10, 2019 at 14:30
  • 1
    I have no idea how you can restart the SSH daemon, I never even heard of this brand of switches. I just suggest what I would try to do on any managed device. If this is the latest sofware version you're on, you should open a support case with the vendor to get these issues fixed.
    – Teun Vink
    Sep 10, 2019 at 14:36
  • 1
    Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer.
    – Ron Maupin
    Nov 19, 2022 at 23:55

1 Answer 1


As stated in the comments you can't solve an problem inherent in the hardware/firmware if there's no update fixing it. Latest firmware seems to be 1.4a and possibly the 5 year warranty isn't over yet, so you could RMA.

However, you can work around - either

  1. replace the faulty device (best)
  2. reboot by scheduled script before the problem comes up (only possible when it's predictable)
  3. reboot by other means if SSH is dead (telnet, serial, ...)
  4. connect the device to a PDU where you can remotely toggle the power; this can also be done automatically by a monitoring script
  • Thanks for your Inrormations. The 1 solution is almost impossible to do, because the Company does not pay money for other Devices. The Second solution. i have already thought it, the problem is, as you say, that it is not always predictable. Serial is very difficult also, because all devices are distributed on different Locatons, Telnet is not safe. The 4 solution looks to be the best. One more question to you. Do you think is it possible to "fix", with a kind of trick, the firmware to bypass the Bug Error?
    – Jim Pap
    Sep 11, 2019 at 9:44
  • @JimPap "telnet is not safe" - no, of course not. You're working around a known fault here, so obviously security is of no concern. If it was you'd dump the faulty switches and replace them (they're EoLed anyway). For fixing the firmware, you'd need to reverse engineer it, find and patch the bug and redeploy. For an excellent hardware hack, that's a 1 to 10 day's job but it may be impossible if the firmware is cryptographically signed (and for normal people anyway). If you haven't got at least 50 of those switches the cost of such a patch likely can't be justified.
    – Zac67
    Sep 11, 2019 at 10:54
  • [...] So, "possible?" likely, "reasonable?" no.
    – Zac67
    Sep 11, 2019 at 10:55
  • we have around 105-110 Switches for this kind of model. I don't know if the firmware is cryptographically signed. But, I think maybe it is worth doing it, since i don't think the Company will change these Network Devices soon. How do you mean to patch the bug and redeploy it. I don't ever try it before.
    – Jim Pap
    Sep 11, 2019 at 11:23
  • @JimPap First, you need to hire the "excellent hardware hack". Everything else is up to her/him.
    – Zac67
    Sep 11, 2019 at 11:29

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