It sounds like you are behind some sort of router and are getting your ip address from a dhcp server, or from your access point. What this means is your computers ip address is 10.x.x.x and everyone elses on your local network is also 10.x.x.x. But when your route off of your network, say to a web page, everyone on your network is using the 216.x.x.x ip. As for the scan it is most likely comming from within your local network or you have ip fowarding enable on your access point.