HELP!!!

HI ALL.
I am new on mikrotik. I have a small ISP here about 100 clients.

I have a problem.

I have two DVR to different places. i configured the first DVR (16 cameras)
the first is connectet from an RB411. from LAN to a switch an than to the dvr
I can access this first dvr from my real IP outside my ISP.

the second DVR (8 cameras) is in another place but is not the same dvr that the one.
I make the same configuration for another RB411 but i don’t use switch.
just i put the lan cable from POE adapter of antenna directly to the DVR.
i cant access it. IF i put a switch i can access it perfectly.

what is the mistake ?
nat configuration ??

please help me
regards

http://forum.mikrotik.com/t/getting-the-most-out-of-this-forum/40983/1
Post configuration and a network diagram