Hi guys. I’m not an IT engineer. I’m just an office manager. Briefly, I accidentally deleted my default gateway (trying to change it into another) with Winbox-> IP-> DHCP server-> Network-> Delete. And now I can’t access my routerboard with winbox, and when I check my IP on command prompt with ipconfig, Default Gateway is empty. I wanted to use MAC address to access, but winbox can’t detect any routerboards, Neighbor section is empty. I tried many times with my notebook connected to the routerboard via port, or to the switch, and tried rebooting both the routerboard and notebook. Nothing did any good. Someone please help me access my routerboard. Thank you.
Solution A: IP
If you still know the IP-Range of the Network,
Give your Computer an IP-Address manually (but not the Routers IP)
Open Winbox and try to connect again
Solution B: MAC
On most Mikrotik-Devices there is a small label with MAC-Addresses.
Open Winbox and try to connect
Try WinBox with the “Neighbors” tab (besides “Managed”), when connected to the same network as the RouterBoard.
If the Routerboard shows up, connect via the MAC address. (Click on MAC address it will be copied to the “Connect To” field.
When logged in with the same user account , try the top-left ‘undo arrow’ , it might just restore the default gateway. (but you rebooted already 
, that redo/undo stack is probably gone)
“Safe Mode” is there to help you with configurations that cause connection loss, by rolling back if connection is lost.