13 - NAT Explained
- Last time very theoretical
	- Ignored NAT
- Going to add in NAT to the picture
	- getting to the end of the all theory sessions
- IP addresses are unique on the internet
	- This is true on the whole internet
	- but on your local network, or LAN, this doesn't have to be true
	- there are 3 blocks of IP addresses set aside as "unroute-able," or unable to be routed over the public internet, for use on LANs
		- 192.168.x.x
		- 10.x.x.x
		- 172.16.x.x thru 172.31.x.x
	- these addresses can be repeated between LANs, just not within a LAN
- If we have these special IP addresses in our LAN, how can we talk to the internet?
- This is where NAT, or Network Address Translation, comes into play
- Your LAN, i.e., your router, is assigned a Public, Internet IP address
	- your router relays the traffic
- In essence, NAT allows for networks within the Network (the INTERNET)
	- One convenient Side effect of NAT
		- all the traffic has to be initiated from the inside out, and incoming traffic must be a response
			- thus, any unrequested packets knocking on the NAT router asking to come in, it has no idea what to do with, so it just drops them.
			- It then becomes an inherent firewall
			- If you need to take incoming traffic, you need to open a port (think of it as a little porthole in the firewall to allow traffic thru) in your NAT router
				- the port forwarding, as it is called, tells the router,
					- send traffic of this type coming in on this port, over to this private IP address on the LAN
			- This whole process, however, can be rather bothersome and annoying
				- A protocol was then created, called Universal Plug and Play, or UPnP
					- it is also called NAT-PnP
				- This is convenient, but it also opens holes for malicious software to do nefarious things to your LAN
					- Thus, it is generally wise to turn this off if you don't need it, and open the specific ports instead
- THEORY IS DONE!
- Command
	- ifconfig
		- going to go over it in more detail later
		- shows you how your network settings are configured
			- IP addresses
			- MAC addresses
			- etc. 
- Bart Busschots
	- bartb.ie <http://bartb.ie/>
	- impodcast.tv <http://impodcast.tv/>
	- podfeet.com <http://podfeet.com/>