I've routed internet traffic of my other systems on this ubuntu linux system where I have configured packet forwarding. but still I am unable to get internet on other systems.
Hence I want to perform packet capture to see if routing is happening correctly and all internet traffic is coming to this system. So that I can find out whether the issue is with Ubuntu system or the router which is forwarding internet trafic to this system. I want all the packets to be captured irrespective of whether that packet was allowed, dropped, blocked.
So how do I do it?