WEBVTT

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-In this solution video,

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we will explore the network configuration

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for our Kubernetes cluster.

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For the first question,

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we have to identify the number
of nodes part

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of the cluster including master
and worker.

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Let's run the command kubectl get nodes.

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Here we can see
that we have two nodes in total.

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What is the network interface configured

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for cluster connectivity
on the master node?

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This is what is used
for our node-to-node communication.

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For this, let's go back to the terminal
and we'll run ifconfig -a,

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which will show
all the network interfaces used.

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This will show you all the interfaces
including the loopback,

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the actual physical interface used
by the cluster, et cetera.

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There's another way to do this in Ubuntu.

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Let's run cat /etc/network/interfaces file
which will open up this file

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and show us the physical interface used.

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Here we can see
that besides the loopback interface,

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the other physical interface available
to the system is called ens3.

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Let's select that as our answer.

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Before we do that, we can also run IP link

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to show all the physical links
on this system.

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Here you can see ens3.

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Let's select that as our answer.

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What is the IP address assigned
to the master node on this interface?

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For this, we can go back
to our ifconfig command.

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We can run ifconfig

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and instead of dash here,
we can just specify the interface here.

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Here we have the IP,
which is 172.17.0.4.

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What is the MAC address
of the interface on the master node?

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Again, we can make use
of the exact same command.

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it is available in ifconfig.

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As you can see for the field called ether,
there is the MAC address.

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We can also use IP link command.

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Type IP link and look up
the hardware address assigned to ens3,

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which starts with 02 and ends with 04.

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Let's select that as our answer,

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which is our option number one here.

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What is the IP address assigned to node01?

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We do the exact same process,
but we'll run it on node01.

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For that we'll run ssh node01,
followed by ifconfig ens3.

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This will fetch the output

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of the command ifconfig ens3

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and print it on the screen.

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We are already on the master server.

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This will just ssh to node01.

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Run that command and it will display
the result on our terminal.

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Here we have the IP address
of ens3 on node01,

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which is 172.17.0.7.

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What is the MAC address assigned
to the nodes01?

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Let's use the same command

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and we have the MAC address
in the same command as well.

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It ends with 07.

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Let's select that as our answer.

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We use Docker as our container runtime,

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what is the interface or bridge
created by Docker on this host?

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Let's run ifconfig -a again

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and that will list
all the different interfaces

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including the Docker bridge,
which in this case is named docker0.

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What is the state
of the interface docker0?

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Let's run IP link.

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It will not be available
in the ifconfig command.

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Let us run IP link for docker0.

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Here, if you look up the status
of docker0 interface, it is set to down.

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If we were to ping Google
from the master node,

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which route does it take?

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What is the IP address
of the default gateway?

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This can be found out
using a single command

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called IP route or IP r.

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What we have to do is look up
the default route,

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which in this case is the very first line.

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The default route goes
through the default gateway

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which is 172.17.0.1

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for our physical interface, ens3.

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We'll select that as the answer.

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What is the port the kube-scheduler
is listening on in the master node?

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There are multiple ways we can do that,

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we can look up at the configuration
of our kube-scheduler,

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which is a static port.

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There's another way
to look at the live port

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which the kube-scheduler is listening on.

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For that, we'll use netstat

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and we'll use these additional flags,

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natulp, p for process,
grep for kube-scheduler.

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This will print the process used
by kube-scheduler along with the ports

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that it's listening on.

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In this, we can see
that in the very bottom of the screen

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of the output,
the port that is used is 10251,

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which is used for my kube-scheduler.

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Look for the listen session

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and here the port
that is being used is 10251.

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That's our answer.

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Notice that ETCD
is listening on two ports,

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which of these have
more client connections established?

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Let's run the same command as before,
which is netstat.

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This time, we will search for ETCD instead

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and we'll look
at the different connections

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on different ports used
by the ETCD port.

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Here we can see
four different listen sessions.

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If you observe closely,
2379 is used the most.

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We also have 2380

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and there is also another port, 2381,

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which is also used by ETCD,

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but the one that is used most is 2379.

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That's because 2379 is the port of ETCD

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to which all control plane
components connect.

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2380 is used
for peer-to-peer connectivity.

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In this case, we do not have
additional master nodes,

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so we don't have multiple sessions
for that specific port.

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That was the last question.

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Thank you for joining me in this video.

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I'll see you in the next one.