Let say, I'm next to a network and can see the traffic (with airodump or similar tool) but can not decipher it (because I am not connected on the network). Is it possible to discover the public ip address of the network ?

I know the MAC address of the users connected on the network but do I know the one of the router ? If yes, maybe there is a way to do the matching. I know IP addresses are not forever but some addresses are static and never change. Maybe there is a database of MAC address having recorded that. Google has a database that match MAC address and geographical coordinates so why not with IP addresses ?

Other idea, if I know where am I, I can maybe guess the IP range used in the city by the ISP (is it findable ?) and then try to "ping" each IP on the range (if it is a /24, it's possible, even /16 maybe). Will I get some information like the MAC of the box or see some traffic on the network ?

These are two ideas I had. I don't know if they are doable, certainly not perfect. Do you think of some others ? By trying several methods, maybe I can get a guess with a bit of luck.

Thank you