Forwarding ports with dynamic WAN IP

RouterOS Beginner Basics
1

/ip firewall nat add chain=dstnat dst-address=69.69.69.69 protocol=tcp dst-port=5900
action=dst-nat to-addresses=192.168.1.101 to-ports=5900

This is an example from the Wiki, where IP 69.69.69.69 represent the WAN address and 192.xxx.x.xxx the local IP. What do I do if I have a dynamic WAN IP? The rule will break as soon as I reboot my routerboard, can I select interface instead of IP somehow, like this for example:

/ip firewall nat add chain=dstnat dst-address=ether1 protocol=tcp dst-port=5900
action=dst-nat to-addresses=192.168.1.101 to-ports=5900

Regards
Event

2

You can set protocol and port and ‘in-interface=public_interface’ to intercept packets on public interface.

3

Thanks mate!