Network Performance Troubleshooting
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Video Transcription
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>> Hey there Cybrarians, and welcome back
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>> to the Linux plus course here at Cybrary.
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>> I'm your instructor Rob Goelz.
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In today's lesson, we're going to be
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covering network performance commands.
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Upon completion of today's lesson,
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you are going to be able to use
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the iperf and iftop commands
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to view network performance.
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The iftop command can display
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a continuous graph of
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the network bandwidth on an adapter.
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For example, we can give it
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an adapter to look at by using
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iftop -i, that i option, and then the adapter name.
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By comparison, the iperf command can
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be used to perform network through protests,
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and we actually have to set that up on both sides of
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the network that we want to test so we can
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set it up on one side as the server
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and on the other side as the client.
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Let's take a look at both of
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these commands with some demo time.
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Here we are in our demo environment,
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today we're going to start with CentOS,
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but we're also going to use Ubuntu,
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>> that's going to be our other system for the other side
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>> of the iperf tests that we're going to run later.
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But first off, let's just go ahead
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and take a look at our adapters,
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and we'll do an IP link show
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to just get our adapter information.
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We're going to use emp0S3
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right here as our guinea pig today.
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What we're going to do next is let's
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make sure that our tools are installed.
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We can do that by ringing the which command,
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if you recall,
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Which will tell us whether or not something is
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installed and where it's located, and in this case,
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we see that iftop is not installed,
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we can't find in any of our path locations.
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If we do a search for iperf,
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actually iperf3, we can do which iperf3,
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we see the same thing here.
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Let's go ahead and install those first,
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right off the bat we're going to do a sudo dnf install,
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and I'll just say -y so that we don't get prompted
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to approve these because we know we want them,
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and we'll just go ahead and kick that off.
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Now, this is just always something important to do.
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Always run that which command
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>> when you land on a system to make sure
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>> those tools are going to be there.
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>> Because some tools, especially performance tools and
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troubleshooting tools, aren't always
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installed on every distribution,
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but we're good to go there.
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Everything has been installed. I'm just going to
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type "Clear" to clear the screen.
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Remember you can also always hit "Control L"
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>> to clear the screen as well.
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>> Now that we have them installed,
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let's go ahead and run iftop first.
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We'll do sudo iftop -i,
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and then we'll use our Guinea pig, emp0S3,
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>> and we'll just let this run for a while.
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>> What we're going to see now is this goes through,
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is it's going to display
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the top network bandwidth usage for
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the adapter in a continuous format
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and update every one second.
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We'll start seeing that on this left-hand side,
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there'll be these bars that will start to climb,
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and they're going to indicate the amount of
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network bandwidth usage that is
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used for each of these connections.
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You can see right now the top thing it's talking to
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is probably the broadcast network.
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It's also sending information back to itself,
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and just sending information all over the network.
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Not super interesting to look at,
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but there is cool information
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>> you can see down here about
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>> the transfer and receive rates,
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as well as the rates of the transmit data,
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and just information up here about the number
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of bits that have been sent to various locations.
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That's all, go ahead and hit Control C,
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we can get out of here,
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and we'll go take a look at iperf.
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Now on this system, we have installed iperf.
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If you're going to be setting up
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iperf3 and using iperf3 for any testing,
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you actually have to install it on
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both ends of the connection.
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Let's go ahead and cut over to
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>> our Ubuntu system real quick,
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>> and here we are in our Ubuntu system.
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What we could do is we could do
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an installation here of iperf3.
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But I believe that I've already actually done so,
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and we can see, as I said,
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when you run which, if iperf3 is installed,
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it will return the location of the binary.
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We can see that it is there, it is installed.
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One other thing that we should do here is make sure
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that this is allowed through the firewall.
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Remember, in Ubuntu system,
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you're going to use the UFW,
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>> the uncomplicated firewall.
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>> For our purposes, we'll just use
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5201 as our example port for our demo today,
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and we can see that that is actually already there.
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We see it says it's skipping adding existing rule,
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so I've already set that up, so we're good to go.
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Let's cut back over to CentOS and make sure we
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have our firewall stuff in places over there as well.
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Here we are in our CentOS system,
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and what we'll do here is we'll run
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a couple of firewall commands.
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Let me copy this here and I'll just
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paste it in to save us some time,
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so that you guys won't have to suffer through
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my terrible typing. But here we go.
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What we're going to run is sudo firewall -cmd,
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>> and then we're going to specify
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>> we want to add that same port, 5201,
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and we're going to add it for UDP,
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and then if that command succeeds,
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which is what this double ampersand means,
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we're going to run the same command,
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but now we're going to specify that we also
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want to add the port for TCP.
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I believe that I've also
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>> already done this on this side,
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>> but let's go ahead and run it, and
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we can see that it's already enabled
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and it's already set up.
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Now we should be able to do what we want to do.
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What we're going to have to do is cut
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back over to the Ubuntu server,
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and we can start that as
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our iperf server to run our test.
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Here we are back on our Ubuntu server,
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and what we're going to do is we're going to start
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the iperf server running on this side for our test.
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When we do this with iperf3-s-p5201,
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we can see that the server is listening
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now on 5201 on that port.
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What we'll do is we'll cut over to our CentOS system,
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which will be the client for this test
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and specify to connect to this Ubuntu system
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>> on that port to start the iperf test.
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>> Back here on our CentOS system again,
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I'm going to copy and paste this real quickly just so
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I don't have any fat finger issues here.
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But what we're going to do is we're going
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>> to run iperf3,
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>> and we're going to specify that we want
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to connect to Ubuntu,
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we're going to specify a bit rate of 90 kilobits,
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and we're going to specify 5 passes with port 5201,
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and I believe that this is integral 10.
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Let's go ahead and hit Enter,
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and we'll let this run.
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This will just take a few seconds here
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to complete running,
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and then you'll see at the very end of it,
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we'll have some statistics
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update and some summary
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about what happened, and there we go.
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We can see that this is completed,
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we can see the intervals,
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and we can also see the bit rate,
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and then down here at the bottom we have
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a summary on how long things took the run,
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how many kilobits per second were
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transferred, all that good stuff,
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and this is not too bad for this connection,
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it's just a little demo environment 2VM,
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so not too terrible math.
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Let's come back over to Ubuntu
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real quick and take a look on that end.
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>> Over here on the Ubuntu end,
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>> we can see that the server is still
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listening on port 5201,
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that's because we haven't canceled out of it.
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But we can see this side of
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the connection and all the information
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that it displays about what happened during our test.
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We can see all the intervals and
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the bit rate and so on and so forth.
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For seeing any problems with network performance here,
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we can try and detect it on both sides,
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>> this connection, by looking at the transfer and
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>> the [inaudible] and the throughput that I've gone through.
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Once we're done, we just hit Control C and that
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will cancel and interrupt this connection.
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If we need to, we can also go back in and disable or
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remove the firewall rules that we've put in
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place to make sure that this port doesn't remain open.
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With that, we've reached the end of this lesson,
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and in this lesson, we covered using
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iperf and iftop,
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if you like, to view network performance.
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Thanks so much for being here,
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and I look forward to seeing you in the next lesson.
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