 The computers in our lab have a look at the back of them and see how many LAN ports there are. Everyone have a look at the back of their computer now. How many LAN ports? So identify the LAN ports. You should see there's a cable plugged into one of them, a yellow cable, and there's two that have nothing plugged into them. These computers have three LAN ports, three wired LAN ports. One is on the motherboard. The yellow cable is plugged into the LAN port on the motherboard that comes with the motherboard, and we've bought two extra PCI cards plugged into the PCI slots for extra LAN connections. So we'll use three of them over the next few labs, not today. By default, we'll use that one on the motherboard, and we'll use the other two for some special purposes later. So these computers have three wired LAN ports. Any other network interfaces? Wireless. We've got a USB wireless adapter here. So in fact, we have four network interfaces, three wired interfaces, and one wireless interface. And there are no others on these computers. Where does the yellow cable go to? There's a yellow cable plugged into one of the network interfaces. Where does it go to? Can you see that? In this lab, we can do things to find answers. You won't break anything. If I say, where does it go to, have a look at the cable and see where it goes to. It goes to the floor, doesn't it? And then where does it go? You see, it plugs into this special adapter in the floor, and you notice, I think, that the floorboards here are raised. They're about 20 centimetres above the actual floor. So we have a raised floor here, and there's cables underneath to make the layout a little bit nicer. So they go into a socket on the floor, and then a special extender cable that goes under the floor and into these four cabinets in the corner. You can maybe open the door in the back cabinet and open this door, and you'll see in, if you open that one, they'll see, they'll see, and you can look at any time, the four groups of nine computers go into one of the four cabinets. So these nine computers, the cables from the floor all come into the cabinet here. The nine green computers go into the cabinet there, and you see in the yellow one in the back, you see all the cables plugged in there. Look in those cabinets, if you can see, it's not easy. How many devices in there? You should see there are four devices in a rack there. The cables are plugged into just one of them. I think the bottom one, that's a switch. So that's a network switch. The cables from the computers plug into that switch, and then that switch has another cable that goes upstairs to a fifth switch. All four of these switches plug into that fifth switch upstairs. Then that one connects out to our router for SIT, and then out to Runxit, and then out to the rest of the world. So that's the topology of the network. This picture's a little bit older. It only has three devices in the cabinet, but our computer has a cable, not two, just one at the moment going into the floor, under the floorboards that runs into these cabinets. In the cabinets, you'll see we're using one switch, that's all we're using at the moment, but there are three other devices there, and the top two are routers, special-purpose routers, and the third one is an old switch. So the one we're using is the newer switch of those. So the top two are routers. So if we wanted to connect and build up an internet, we would use those top two devices. In this course, we would not use those other three devices. Because it's hard to get access, it's hard for students to walk up and plug cables in, so we will use our own computers as routers in later tasks. So that's just the physical topology of our network. We have nine computers connected into a switch, and those four switches connected into another switch. We're all on the same LAN, all on the same subnet, and in fact the MAC lab upstairs is also on the same subnet. So from the internet perspective, we're all on one big cloud, one big subnet for this lab and the MAC lab. So we want to learn some commands that show us more information about our network setup. So we said how many wired interfaces? We said we have three wired interfaces and one wireless interface. What's a command that shows us the configuration of our interfaces? Try. Try the command that I've used and shown you many times. How to see the config of your interface? Short for interface is IF. IF config. Show you the configuration of your interfaces. And for me, I'll just pipe mine through less so that we can scroll through. You don't need to. This shows you from the operating system perspective what interfaces this computer has. And you note some names there. ETH0, ETH1, ETH2. ETH short for Ethernet. The common name for wired interfaces. So there's three interfaces for the wireless card, the wired card, sorry. LO, what's LO? Local or loopback. This is a special interface for testing when you want to send to yourself. So this is not a hardware interface. This is a special one set up by the operating system. If you want to send something to yourself without sending out on a cable or a wireless link, you can send to the LO interface called the local loopback interface. And you may recognize the IP address there. This special case address 127001. So that's a special case interface. Where's the wireless interface? Can everyone see theirs? No. You can only see your three wired interfaces. IF config doesn't show interfaces which are turned off. If you want to show all interfaces, use IF config minus A. Show them all. And you should see WLAN there, wireless LAN interface zero. You can plug in multiple wireless LAN adapters and you'll get... Usually the operating system we've set it up so it labels them zero, one, two and so on. And the way that we've set up these computers is assuming everything's correct, EDH0 is always the network interface on the motherboard. This is a useful one to remember. EDH0 is on the motherboard. EDH1 is the top PCI slot. EDH2 is the bottom PCI slot. Zero, one, two, physically. Because later when we plug cables in we'll need to know which one we're using. So the operating system gives them names. If we want to look at just the config of one of them we can specify IF config EDH0. Another tool is... So this shows the operating system's perspective of this interface. We can also get a bit of information about the hardware. So it's actually a piece of hardware on your computer and one tool that gives us something about the Ethernet hardware is EDH2. Followed by an interface it tells us some information about that hardware associated with EDH0. And I'll pipe it through less because I know it has a lot of output. So that's some information about the hardware device. IF config is about the software configuration. Have a look through that information. Try these two tasks. See if you can find some of the information I list there. So just from those two commands they give some information, just browse through. You don't need to understand everything, especially from EDH2 but some of the things you'll quickly recognize. And especially look at the output of IF config and see if you can complete these two tasks. Find the information, then put a file on my computer named by your computer number. Bonus for the first person to do it in a short time.