Hey guys, welcome back. In this video we are going to get to some practical
networking things, and this is all in terminal. And so the first thing we're
going to do is bring up terminal, and first I want to talk about the ping
command and what this means and what it does. So, you can ping an IP address or
a domain name to see if you can get a successful response from it. This is a
great way let's say you're using a web, this is just an example, if you're using a web
browser and you're trying to troubleshoot if the web browsers isn't
working or if your entire internet connection is not working, you might drop
down here to command line and run a ping command on a known host that you
know is always going to be up, for instance google.com. And so that's
exactly what we're gonna do, so I'm just gonna type in the command ping and
then the address of what I want to ping. And I'm getting a response and it tells
us what length of time each response is taking to return to us, so
yeah. It also shows other stuff like the exact IP address, the
server that it's reaching, and that good stuff. And this is gonna just
go until you close it, so just CTRL+C to exit, and then it gives you a breakdown
of what happens. You could let this run for a while to see if you're getting any
packet loss through your network card, and so that's what pinging does. So I'm going to
clear this up here and we're going to talk about the command ifconfig. So, on
Windows in command line you have a command called ipconfig and it spits out a
whole bunch information about your network configuration. In Linux it's
ifconfig and it does the same here. I'm gonna run that command again. Alright,
so this is going to link our addresses here or our network interfaces, and also
any IP addresses that it has and whatnot. So, the first one is gonna be an ethernet
which I don't have plugged in right now, and so it's gonna be basically not working. This
is the name of that interface. This is our local loopback, so this is like a
virtual interface that runs that it has our local host address here and it
basically controls that, and then down here we have our wireless ethernet
which we can see this is working as I have received bytes. So, "RX" basically
means what you've received, "TX" basically means what you've transferred out. So, that's how
to read that. There's an IP 6 address right here and my IP address, this is
gonna be my NAT address and it gives ID's and stuff of the network interface
device. And so that's basically how to use ifconfig, sometimes this might be
useful to see if you know you're getting a valid IP address from the router, to see you
know if it's actually working at all which you can see here
mine is. I'm gonna clear this and what we're going to go over now is a command called
TCPDUMP. It's a really powerful command line packet sniffer, so it can analyze
the packets that are you know going in and out of your computer or your network.
So, first thing we need to do is install it if we don't already have it installed.
So, "sudo apt-get install tcpdump" it's probably already installed but just in case make sure,
and it is it's the newest version. So, this is a big command-line tool and I was gonna
do more stuff in the video but I think we're going to cut it off after this
command. So, what we're gonna do is basically just run the command "tcpdump"
We don't have permission to capture on that device so we're going to run "sudo tcpdump"
And this capturing all packets that are coming in and out of my my computer. This is just gonna run until
you cancel, so I'm just gonna cancel here. Now, as you can see that was a pretty big
output and so what we can do is we can only capture a certain amount, so what
we're gonna do is that. How we do that is basically using the command
"sudo tcpdump -c 10" and that's good. Alright I have to run sudo.
So, this is going to capture 10 packets.