Basics of ipconfig, ping, tracert, nslookup, and netstat

A quick tutorial to introduce basic network testing tools like ipconfig, ping, tracert, nslookup, and netstat. Cisco CCNA 1
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you're going to want to know your basic
network testing tools introductory to be
able to test your network for comic 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
Trey cert or trace our tea or trace
route
nslookup and netstat so let's run
through an example of all these commands
ok 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 ok 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
ok IP address subnet masking 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 IP config
space / all if we put in that command we
can see our host name
we can see our physical address right
here which is our the mac address of our
Nick of our network interface cards or
ethernet card has this mac address
burned into it we can see the dhcp is
often that we have our subnet mask we
see our gateway and our dns server
information
ok and this is once again using just an
XP client
it's probably gonna be a lot more
information if you do this in there will
be more information if you do it in
windows 7 or windows vista cuz you'll
see
IP version 6 information and you'll
probably see more interfaces but this is
a very simple client for this example
ok so that is ipconfig ipconfig all very
useful
you'll need to know those tools next
ping
you're going to need to know how to use
the 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 a 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 then
come back our echo replies and sometimes
you can have a situation where you
picking 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 being blocked
another thing about pingas you can ping
domain names too
now when you pick a domain name there's
going to need to be a deal domain name
server to be able to resolve the name
so like if I ping yahoo.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 resolve DNS I can go out
across the internet and come back in and
so that's pretty useful a lot of sites
from ping we can also do a traceroute
now trace route will show us almost like
a ping but much more detailed as the as
the requests for replies travel across
the Internet each router along the way
we'll send a reply or send a message
back and so will be able to see every
router along the way
send a return message so i can say ping
me not paying trace our tea or tray cert
and i'll do the same thing due to
yahoo.com is an example
and as this trace command get sent out
over the internet you can see all of the
routers or hops along the way of
communicating back and you can trace
that here and if there's a problem in
communication breakdown you can see
we're 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 which router is
blocking your communication
ok so that's Trey cert all right let's
see here what else it is we want to
cover
nslookup we're now going to cover to
look up resolve domain name to an IP
address and the netstat to look for open
ports so let's do that right now
ok 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
trace our tea or tray cert 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 NS
lookup right name server look up and put
in a space and type yahoo.com and my dns
server that I have configured will try
to resolve that name
and so it's said that basically at four
. one there was no dns server but at 50
. one we have one
so there's miss configuration their
writer passed it on to 50 . one and we
got this reply that yahoo.com resolves
to these IP addresses all right
and we can actually change our nslookup
we can just type in this look up and run
the program and then set a separate
server for to use the testing with so i
could say you know server change it to
50 . one
all right and it says there and then i
can say resolve yahoo.com right
and then there's not an authoritative
answer why is it a non authoritative
answer because 50 . one is not the
authority for this domain name
it is not the primary dns server for
this domain name
ok all right let's do the next one
all right 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 - hey for all you'll
see all of the port's that this computer
might have listening to 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 these as we make
connections or have extra listening
connections happening over here
right you can see that we're listening
on certain parts already but we want to
do something cooler for the test so i'm
going to run
a sample k ftp server and let's roll run
a will run a HTTP server so we have a
web server here
right so I've got a web server waiting
and I've got a ftp server now active
I'll close this window and so now if we
run a netstat - all we should be able to
see those servers those ports listening
on our computer and you can see right
off the bat 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 too p
all right
this is without names so i did a /a n
and now you can see the port numbers so
you can see here that um 21 is listening
listening on 000 meaning every listening
on zero zeros are listening for every
incoming address on port 21 because it's
running an ftp server port 80 000
listening for any incoming address on
port 80 for the web server so very
useful tool to see which connections are
established in which are simply
listening and which are waiting and
network basically channels that your
computer is communicating on