Hello!
Sorry for my english.
I have a problem.
My router is Mikrotik RB-750G. I have tried to upgrade RouterOs on It to 5.12.
I followed instructions in manual on this page:
http://wiki.mikrotik.com/wiki/Manual:Up ... ing_Winbox

I just copied routeros-mipsbe-5.12.npk via WinBox and then rebooted.
After that router always reboots, a I suppose: net link (to which ethernet cable connected) is blinking, then all leds are flashing simultaneously and off. And my computer trying to get IP via DHCP, then It doesn't and sayig that cable unplagged. And again and again.

So I'm trying to update RouterOS with BOOTP. I have generated virtual machine with RouterOs 4.17. Have puted routeros-mipsbe-4.17.npk on It. Tuned DHCP. Then I see in logs, that my device getting ip, getting access to file, then closing connection, and I see that It reboots again. And so on. By the way my device gets IP only if It connected via 1-st interface. Other don't even get IP.

By the way, I have serial cable from Cisco (on one side It have RG-45, and on other COM). Can It help? I just don't understand how to connect by serial console if It possible at all.

So, what is yours advice?
Thank you.

Hello.
It`s still actual.

start with easier solution - reset the device according to manual:
http://routerboard.com/pdf/295/rb750GL-qg.pdf

Of course, I've tried to reset with button and with jumper.
I've already compiled elf image. With this file in BOOTP device doesn't reboot. But It still offline. No pings, no connection in Winbox, even by phisical adress and device not found in Netinstall. But when i'm trying to ping device I see link activity.
I've tried to use network scaner, but device wasn't found.
I fell, that It's alive, but something disturbs me... I don't know what...
May be you have suitable elf image for 750?

no need to compile ELF image, use Netinstall!
http://wiki.mikrotik.com/wiki/Manual:Netinstall

Thank you!!!
I saw this page before. But It didn't turned out.
But today I had tried again and my router is alive again!
I don't remember how I did It previosly. Possible, that my mistake was in addressing or in procedure of calling booting from PXE. Or maybe in that, that I didn't knew that Netinstall have It's own PXE server, and I started It on another machine in network. So there was conflict.
Not everything was clear for me in documentation.
As they say "there's no evil without good". I had read many docs and now I know more technical details of this device.

Thank you, normis, for returning me to the right way.

glad that it worked!

It may just be a coincidence but I had the exact same issue with upgrading my 750G to 5.12. After using NetInstall (and reverting to 5.11), the router was brought back to normal.

The 5.12 npk file I downloaded matched the published MD5 hash and was successfully installed on a 411U before being used on the 750G.