I have two routers in public internet and add strict firewall rules that drop any traffic from unknown source address. Router A has dynamic pppoe ip address got from ISP. I want to notify the new address immediately to Router B whenever the ip is changed. So I need a knock-door mechanism such like sending a particular size packet to a predefined port. I found the traceroute tool may match my request, but it is time consuming for me. DDNS is also not a real-time solution. Does mikrotik have direct sending customized packet method?