This is one of multiple troubleshooting videos.
We've been told that switch one on the left in this typology is not able to ping switch to ON THE RIGHT.
In this typology now in apology I'm using physical devices rather than three.
I'm only using Janus three to show a diagram of the topology.
So let's verify what we've been told on which one can we ping switch to.
It looks like we can't.
The pings are failing.
So let's do some troubleshooting show IP interface brief.
Can you see the problem here.
What's wrong in this output.
So here's the command to show IP interface brief what's wrong.
Notice fast Ethernet 0 3 is down down show interface.
0 3 we told us that the interfaces down the line protocol is down.
It's not connected.
Now at this point you may need to check the cabling to see if there's a problem.
But before you do that let's have a look at the connection on the other side.
Some brought a one show IP interface brief on the side.
The interfaces up down show interface zero
in the south but we can see that first Ethan at zero is up or down on the side.
First Ethan it is 0 3 is down down.
Now based on this output what's the problem.
Can you see an issue between the switch and the Rodda based on the output.
So before walking and checking the physical cabling or getting someone else to check the physical cabling
What can you see that's wrong in this output.
OK so notice this full duplex or 100 megabits per second on the side.
Notice auto duplex 10 megabits per second.
It looks like there's a problem with the speed and duplex configuration on the side a mac address and
an IP address have been configured on the fast ethernet interface and the speed of the interface is
10 meg on the side and the output we can see that it's using full duplex 100 make the second.
So if we look at the interface configuration notice the speed and duplex have been hard coded.
Typically today you wouldn't do that but let's say for example that we set the speed and duplex to 100
make.
So on the side we set the speed to 100 meg.
Notice you can see that the interface came up and then went down and we are seeing another problem duplex
mismatch.
And we can see that on both sides we are told that first Ethan it is 0 is using half duplex and on our
side we're not using half duplex so show run interface if a zero speed is 100.
What you probably want to do is set this to do or to negotiation rather than hard coded so that they
can negotiate properly and on the side
we probably want to do the same show run interface if zero slash three rather.
So let's set the speed to order and the duplex to order.
So that's automatically negotiated with the other side.
Here we still seeing problems with speed and duplex show run interface f 0.
Everything is set to auto and on the side show run interface 0 3.
Everything is set to Auto Show interface if 0 is than 3.
We can now see that the interface has come up up.
It's connected.
Show interface.
If a zero interface is up up so that looks a lot better.
So it looks like we've solved a problem between switch 1 and router 1.
We didn't have to check the physical cabling.
The problem here was that the speed and the duplex were wrong.
Ok so can switch one ping switch to.
We're still having a problem.
We see us in the output.
In other words unbreachable show running come fake
which doesn't have a lot of config on it.
But what it does have is an IP address configured locally and the default gateway so it can be paying
the default gateway.
Yes we can so disable IP domain look up to speed up trace rot and if we trace to 10 1 3 to notice we
get to 10 1 1 1 but we don't get any further.
So it looks like the traffic gets too broad of one but we're receiving an unreachable message because
one doesn't know what to do with a traffic.
So he has brought a one show IP ROFFT.
Can you see a problem here.
We only have a route for Ethan at zero.
There's no routes to get to such to show IP protocol.
We are running the GOP on the router and it's enabled on all interfaces.
So show run section you GOP has the GOP configuration that looks good.
Show i.p your GOP interface the GOP is enabled on fast Ethernet Zerah as well as serial 0 shows ETP
neighbors.
We see SCDP neighbor relationship to switch one but we don't see SCDP neighbor relationship to switch
to CGP allows us to check laya to connectivity if CTP is working.
It means that layer 1 and layer 2 are working that at the moment it looks like layer 1 and layer 2 are
not working.
So lets check show IP interface brief.
Can you see the problem.
Notice serial is zero.
He's up and down.
There's a problem with the physical link between Rodda one and router to on it to show IP interface
brief.
We have the same problem here.
Serial 0 is up and down.
So now would be a good time to check the cabling.
Fortunately with serial interfaces we can use the command to show controllers serial and specify the
serial interface number to check whether a cable is connected to the router.
In this case interface serial 0 has a DTV cable connected.
It's a thirty five cable.
But notice the problem the clocks are stopped on the side show controllers.
Cereal is zero.
What's the problem here.
What's wrong and how do you fix it.
OK notice here we've got a thirty five DC cable and there's no clocking on the cable show run interface
serial zero clocking hasn't been configured on the cable
on a DTV cable.
You don't use the clock rate command.
So I could specify a clock rate but that command is going to have no effect because this is a DTV cable.
But on this side if we enter the clock rate command and notice there are different clock rates available.
I'm just going to use 64 K show run interface serial 0 noticed the command is retained in the running
config and that's because the interface here is a DC interface so shoyu IP interface brief interface
is now map up on the side we saw a neighbor relationship established in your job.
We also saw the interface come up.
So show IP interface brief.
The interface is now up up show controllers
cereal zero on the side.
We now see that transmit and receive clocks are detected on the side show controllers serial 0 the clucking
is set to 64 kilobits per second because the side is the DC side of the cable a back tabac cable is
connected between Rodda one and router to
and router two is the DC side.
So it needs to provide the clocking for the connection.
So show CGP neighbors we now see router two as a neighbor of one ping ten one to two.
We can ping Rodda to show up at your job.
The neighbor we can see rodded to as a neighbor and hopefully switch one will now be able to paying
switch to which it can to confirm that I'll use the command debug IP ICMP on switch to and ping from
which one to switch to and we can see that an echo reply was sent.
Switch to can also paying switch one.
So we've successfully resolved two issues in this network.
Be careful when troubleshooting.
It's a good idea to know us-I model and split the troubleshooting ping trace route in CGP are useful
for troubleshooting networks.
It's important that you learn your show commands don't just type a show run on a device learn how to
use show commands to see the state of interfaces so as an example here we can see that the interfaces
up will be able to see other information on the interface such as the load packets sent and received
and so forth.
If I removed the clock rate on the interface by using the common clock rate what we should see on Broadway
one is that the interface goes down it stays up for a while because of the keep alive which is set to
10 seconds but after a while as you can see that your GOP neighbor relationship went down and what we
should see is that the physical interface goes down after a while
like that.
So the interface has just gone down.
Show interface 0.
Notice interfaces up down.
So learn to use your show command to see what's going on on the network so show controllers serial zero.
Here we can see that a cable is connected but we're not receiving clocking
clocking a set.
This will change as you can see here transmit and receive.
Clocks are detected interfaces come up show interface serial zero.
We can now see that the interfaces of pop one of the most important skills for use a network engineer
is to learn how to troubleshoot networks.
Hope you found this video useful if it's been of benefit to you please like it temperedly subscribe
to my YouTube channel.
I wish you all the very best.