>> Perhaps you've created flows from our LAN network range only? If so, for a >> ping to work, you need to specify the local IP, like >> ping -I 192.168.1.1 192.168.2.1 > how to change the source address for the 'netcat' command payload?
According to http://www.openbsd.org/cgi-bin/man.cgi?query=nc it has a similar flag, -l nc -l 192.168.1.1 192.168.2.1
