You're going to want to know your basic network testing tools introductory. To be able to test your network for connections, to see if you have connectivity to your server, to see if you have connectivity to your gateway, your router, and you're going to need to know how to use these few commands here. Ipconfig, ping, tracert or tracert or trace route, nslookup and netstat. So, let's run through an example of all these commands. Okay, I'll close these windows and I'll open up a command prompt and we'll start off. I can make this a little bit bigger. Make the font a little bit bigger for you, so it's easier to see. Okay, so now that I have the font a little bit bigger, I'll run an ipconfig. And what can you learn from by running an ipconfig? Well, you're going to be able to get your IP Address, your Subnet Mask and your Gateway. So, and this can be useful because if you've set your computer to Dhcp client to automatically obtain this, you can't see it by going to the nick and right clicking and looking at your properties. You won't be able to see what IP Address you received. So you need to be able to do this to find out what is my IP Address. Okay, IP Address, Subnet Mask and Gateway. But, we don't see our DNS server information. And we also, there's a couple other things we can see if we put in ipconfig space slash all. If we put in that command, we can see our host name. We can see our physical address right here which is the mac address of our nick, of our network interface cards. So our ethernet card has this mac address burned into it. We can see the Dhcp is off and that we have our Subnet Mask, we see our Gateway and our DNS server information. Okay, and this is once again using just an xp client. It's probably going to be a lot more information if you do this in. There will be more information if you do it in Windows seven or Windows vista because you'll see IP version 6 information and you'll probably see more interfaces. But this is a very simple client for this example. Okay, so that is ipconfig and ipconfig all very useful. You'll need to know those tools. Next, ping. You're going to need to know how to use ping command to be able to test to see if you're connected on the network. And mainly if you can, let's say get a response from your router. So in this case, I'll say ping and then I'll type the IP Address of the router. So, I'll say the Gateway 192.168. And I'll put in the IP Address of my Gateway and you can see here that I'm getting a reply from the Gateway. And that means that I have communications established with the Gateway router and that's a very useful tool. Be able to ping another computer on your network and see if you can contact them. Ping uses ICMP protocol and sends out an echo request and then the packets that come back our echo replies. And sometimes, you can have a situation where you're ping a computer and you actually have a situation where your firewall could be blocking those pings. Your pings, your echo request could be getting to the destination but not coming back because it could be ping blocked. Aother thing about ping is, you can ping domain names too. Now, when you ping a domain name, there's going to need to be a domain name server to be able to resolve the name. So if I ping yahoo dot com, this is going to test, not if I can just get to my router and back, but it's going to test to see if I can get all the way to yahoo's web server and back. So it's going to go across the Internet of over multiple routers to get there and then return. So you can see there I can get a reply, that shows that I can't resolve DNS, I can go out across the Internet and come back in. And so that's pretty useful. A lot, Asides from ping, we can also do a trace route. Now a trace route will show us almost like a ping but much more detailed as the requests for replies travel across the internet. Each router along the way will send a reply or send a message back. And so we'll be able to see every router along the way send a return message. So I can say ping, I mean not ping, tracert or tracert and I'll do the same thing. Do it to yahoo dot com as an example. And as this trace command gets sent out over the Internet, you can see all of the routers or hops along the way communicating back and you can trace that here. And if there's a problem in communication or break down, you can see where at which router, where did the communication breakdown. This can be useful if you have multiple routers on your network and you want to know where, which router is blocking your communication. Okay, so that's tracert. All right, let's see here what else it is we wanted to cover. Nslookup, we're now going to cover to look up resolve domain name to an ip address and then netstat to look for open ports. So let's do that right now. Okay, for nslookup, we're trying to resolve a name to an ip address. So, you see that when we last pinged yahoo or we did a tracert or tracert to yahoo that we got messages back but basically behind the scenes, DNS was resolving those names to IP addresses. Well, we can put in a command to find those IP addresses straight up. So, I can say nslookup, name server lookup and put in a space and type yahoo dot com. And my DNS server that I have configured will try to resolve that name. And so it's said that basically at 4.1, there was no DNS server, but at 50.1, we have one. So there's a misconfiguration there. Router passed it on to 50.1 and we got this reply that yahoo dot com resolves to these IP addresses, all right? And we can actually change our nslookup. We could just type nslookup and run the program and then set a separate server to use the testing with. So I could say a server changing to 50.1 All right? And it says there and then I can say resolve yahoo dot com, right? And then there's a non-authoritative answer. Why is it a non-authoritative Answer? Because 50.1 is not the authority for this domain name. It is not the primary DNS server for this domain name, okay? All right, let's do the next one. All right, I'll clear that screen. And last but not least, netstat. Netstat is useful for seeing whether we have listening TCP ports or connections on our system, network connections established or listening or waiting on our system. So, if you type netstat, let's say dash a for all, you'll see all of the ports that this computer might have listening, you see. And so you can see here local address. This is the Protocol, TCP protocol, UDP. This is the local address here, the foreign address here and then the state whether it's listening or established. So let's see if we can run some services and then watch as these, as we make connections or have extra listening connections happening over here, right? You can see that we're listening on certain ports already, but we want to do something cooler for the test. So, I'm going to run a sample. Okay, FTR Server. And we'll run a HTTP Server. So we have a web server here, right? So, I've got a web server waiting and I've got an FTP Server now active. I'll close this window. And so now if we run a netstat dash all, we should be able to see those servers, those ports listening on our computer. And you can see right off the back, TCP, FTP is listening. And you can see here that http, this is port 21 listening and this is port 80 http is also listening. And pretty cool. Let's see if we can do that to p. All right, This is without names. So I did a slash an. And now you can see the port numbers. So you can see here that 21 is listening, listening on 0.0.0, meaning every, listening on 0.0.0 listening for every incoming address on port 21 because it's running an FTP server. Port 80.0.0.0 listening for any incoming address on port 80 for the web server. So, very useful tool to see which connections are established and which are simply listening and which are waiting. And network basically channels that your computer is communicating on
