I got a Mikrotik RB450 using at my office. The problem is sometime the router like hanged and caused some of the users still can browse and the other can’t browse. The I unplug the routerboard, it beeps a long beep like 1-2 second before power down and the same beep sound after the routerboard power up. I think the routerboard must have a problem, but I cannot found anything in the internet about that.
Anyone can help me with that problem?
Hi,
if you disconnect the board its impossible that you hear any sound.. 
It’s possible that you have something connected in ether1 giving PoE to the board and a diferent power supply in the jack? If it’s like this, make sure the 2 power inputs are different: 12V and 18V for example.
I got PPoE connection in ether1 for sure, is that causing the beep sound? Before it’s powering down there’s a long beep sound like a UPS failure.
I’m using 12V external adaptor for powering the routerboard, is that also a problem?
Is it normal if it beep that way? After it boot there’s a long beep like before it’s powering down and then a normal short beep.
Make a RMA..