FTP server behind multiwan with load balance

RouterOS Beginner Basics
1

Hi everyone!

I have 3 WAN load balanced with something adapted from
http://forum.mikrotik.com/t/howto-dual-wan-pcc-with-dynamic-ip/101969/1
The problem is that I have one FTP Server behind the router and I can’t fully connect to it.
I’ve added (on top)

/ip firewall nat
add action=dst-nat chain=dstnat dst-address=<WAN1IP> dst-port=21 protocal=tcp to-address=<FTPSERVERIP> to-ports=21

and I try to access with one IP (WAN1 IP, the one used by IP/Cloud to get the URL).
I have to connect several times in order to actually connect because most of the time I get a timeout or a refused. Also when I’m connected and trying to list contents, sometimes I also get denied.
I’ve tried adding “Dst. address” and “In. Interface” to the NAT, but I get the same results.
What’s wrong with the setup?

2

Read wikipedia about FTP. It has more than one connection by design so related connection (data connection) probably just goes through another WAN.
You can try to switch passive/active mode in FTP settings.
More robust design is to mark ftp server traffic in mangle and bind it to single WAN.

3

Thanks for your answer!

I have lots of clients using the server and some aren’t tech savvy so I don’t want to force them to hunt for the PASV setting. I’ll try to solve it configuring the router first. I had a TPLink TL-R480t+ that worked so I assume I can make this Mikrotik work as well…

Ok, we are heading somewhere with this. I can mark port 21 but, how do mark the data coming from an unknown data port?

4

Make all traffic from this pc go through only one wan by src-address so no load balancing for this pc