DNS, and DNS pass-through:
	Already went through this with 435 - sorry if you're in both
	Let's take a quick look at what's in a DNS query!
	Interpreting a header with a C struct:
		Kinda like those old keyboard overlay things
	
A summary of last time:
	We set up orcrist with NAT and bridging
	For this kind of thing, I suspect NAT is more common
	Still, you can do either
	Note:  FreeBSD and Linux support RIP
	I have NAT set up on nimrod for stuff
		Let's take a look at the script that sets it up
		Although I don't think I actually have it configured that way!
		Let's look at the routing table
	Why?
		Limited number of networking ports available
		Defeat MAC address based security
		Protect a machine with vulnerable open ports
		Limit a machine's access to the network
		Put a machine on wifi that only has wired 
		Probably some other use cases out there

A bit of a think-through:
	What's the router do when it receives an ethernet frame?
	Ignore it?
		If the CRC is wrong
		If the MAC address doesn't match that interface on the router
	De-encapsulate and take a look at the IP address?
		"de-encapsulate" = "look at the data part of the ethernet frame"
		It's not like you have to decrypt it or remove anything
	In C, it's probably something like this:
		char* ip_header_start = frame_start + frame_header_size;
		struct ip_header *iph = (struct ip_header*)ip_header_start;
		// After this, use iph->destination_address or whatever to get fields
		Kinda, anyway.  Linux, for example, uses a struct sk_buff for socket data
	Decide where the packet should go
		Depends on our routing rules
		Destinations, subnet mask, etc
		Need to know what interface to send it out, with what destination MAC
		Remember:  We can't send anything without a MAC address!
	Re-encapsulate, and send it out the selected interface
		Efficiency note:  Can probably just amend the frame header in-place
		Remember to decrease TTL
	Do we want to log it?
		Probably not!
		Logging could quickly become the limiting factor for performance

We've been adding some very simple routing rules!

Next:  Setting up this kind of thing on Cisco equipment
	Packet Tracer!

A quick question to address:  "isr" in "Cisco 4331 ISR"
	Integrated Services Router
	We can put a switch module in it
	Might be other modules too, that I don't know about
	
Alright, the configuration:
	Three routers on different networks
	Let's go Internet-routable this time
	One router to go between each of them
	This'll be a bit big, as far as configurations go

Lab today:
	https://blog.certskills.com/clab118
	Yes, it's a lot of entering routes
	Learn appreciation for RIP, OSPF, etc?