Dear MikroTik Forum Members

I am facing a problem. My 951Ui-2HnD randomly reboots when some client connects to the router. It happens on its own. When some new client connects to the router it randomly happens. At times it wont reboot. But on other times when some one connects to network suddenly my router reboots.

I have checked many times. Checked all my configurations many times. Tried different settings. But cant figure out what is causing this. Tried assigning static ip to my clients as well but it wont help either.

This random reboot problem started occurring since when I have connected a new TP-Link router to ether port of my mikrotik router. I use this new router to extend my network.

To check the problem I removed the new tplink router and guess what. Random reboots stopped. And router starts behaving like everything is normal. No more random reboots. At this you might think that the problem lies in my new tp-link router, but I got another brand new tp-link router to test. But same random reboot problem started with the second tp-link router as well. I have tried it with an old different model router as well. But same problem. So this means the problem lies within mikrotik (either software or hardware).

To further check I changed the settings to another ether port but same problem reappeared.

Another check I did was totally removed new tplink router and instead connected one of my spare laptop directly to an ether port of mikrotik. And guess what. Problem started again. Same random reboots. And this time reboot occurred even when no new client connects. It almost look like the mikrotik router just randomly decides on its own when to reboot. Sometimes it just reboot even when i sit idle and do nothing from the connected laptop. Winbox just kicks me off and LAN signal from windows taskbar disappears. And when router completes it reboot cycle everything starts working again normally. (Until next random reboot)

The duration between reboots vary. It ranges from few minutes to few hours. Yes its completely unpredictable. It can reboot within 5 to 10 minutes. And sometimes it takes hours like 10 hours until it reboots again (or if some new client connects in between, then it reboots again). Remember its not always reboot when new client connects. It just decides which one it likes and which one it don't like and reboots.

Enough of the explanation i think. I tried my best to describe the problem. Its so annoying. I have researched everywhere on internet but cant find a solution of this problem.

Please let me know if you need any more information. I can share the export=file backup with you guys if needed.

Thank you

Did you try to replace power adapter with another one? It can be 12V or 24V - just make sure it can supply enough power (at least 1A uf 12V or at least 0.5A if 24V).

If power adapter is starting to fail due to age (perhaps capacitors inside dried out), it might not be able to supply enough power and additional power draw due to another ether port being used might cause voltage drop low enough to reboot the device.

Thats the idea I never came up with... It could be it.
On the adapter it is mentioned: OUTPUT: 9v and 700mA
I will buy another new one and check if it solves the problem.

Shall I buy with similar Output or do you recommend some other Output settings?
I will update the results after testing.

Thanks for help.

Your router has rated max power consumption of 6.5W ... your current power supply provides up to 9V*0.7A=6.3W, so even when brand new it was a tad too weak. Device can take 9V-30V on input, so your current power adapter is on the lower end. If it drops voltage only so slightly due to overload, the supply voltage will drop below specified minimum and a reboot is expected.

Specifications for your device state that they ship with 24V 0.8A power adapter. So when looking for new power adapter, go for one with similar specs. Get one which can output at least 10W (the supplied one can output almost double).

If the larger power supply doesn't work try upgrading the firmware "/system routerboard> upgrade". I had one of these 951's that was randomly rebooting, the upgrade cured it.

Thank you for the upgrade suggestions. Forgot to mention before. Yes system firmware and all packages and software are upgraded to latest stable version. 6.44.3 at this time.

The good news is. I have purchased and installed 12v 1A adapter power supply and since last 16 hr not even a single reboot.

It looks like problem has solved.

Really appropriate your help and suggestions in this matter. Now since this case becomes the part of forum and discussions, I believe it will help anyone else with the same issue.

Thank you guys. Bye.