This is one of multiple videos that help you troubleshoot CCNA scenarios in preparation for the CCNA
exam.
We're going to look at how to troubleshoot multiple issues with telnet in this network.
So let's get started.
On router 1 telnet to the loopback of router 2.
We're told that password is required, but none is set so we're able to telnet to the router but then it's
immediately disconnecting us.
So on router 2, show run pipe begin VTY.
On the VTY line, we've got a command called Login, Login means that the VTY line requires a password.
Notice we're told that password is required, but none is set.
So password needs to be configured on the VTY lines.
So password Cisco,
let's try again telnet from to router 1 to router 2, we now get a password prompt and if we put the password
in correctly, we can login.
Second problem, when we try to go to enable mode, we are told that no password is set.
So show run pipe include enable.
What you'll notice in the output here is that there is no enabled password.
So run include enable.
No output.
What about secret?
No secret password configured, so enable and we could set a secret or an enable password.
Let's set a secret because that's better.
So we'll just call the Cisco.
When we type enable now, we prompted for a password and we can log into the router, so let's test that
again back on router 1, Telnet to router 2 can log in and we can go to enable mode.
So we've solved the problem on router
2.
What about router 3? I'll telnet to the loopback of router 3.
We're told that the connection is refused by the remote host.
Can we ping that loopback?
Yes, we can.
So this is not an IP connectivity problem.
This is something else.
On router 3, show run pipe begin VTY.
Now, these pipe commands may not work in the exam, so just type show run and then scroll down to the end
of the config to see the VTY configuration.
So you might have to do show run and press spacebar all the way down until you see the VTY config.
Can you see the problem?
Notice here, transport input SSH we're using telnet, but the lines have been restricted to only using SSH,
which is better in the real world
But here we want to be able to telnet so we could specify all which would allow all protocols.
But from a security point of view, we may want to enable only SSH and Telnet.
So show run pipe begin VTY.
So both telnet and SSH are allowed on the VTY line.
Once again, let's see if we can telnet.
We are able to log in to router 3, so we solved the problem on router 3.
Now, what about router 1, can we tell Telnet
to router 1? Says connection is refused, can we ping router 1?
Yes, we can.
So we need to go back to router 1.
Let's have a look at the configuration.
I'm going to scroll through the config, see if you can find the problem.
So there's the IP address on the loopback.
Can you see a problem?
Notice this,
access class 1 in, an access list has been applied to the VTY lines
and scrolling up through the config, it's only permitting the loopback of router 2.
When you telnet, it's using the outgoing interface as the source of the Telnet connection.
Now, we could specify source interfaces and try and use the loopback as the source
but for CCNA that's not required.
What we want to do on CCNA is either remove this access list or edit the access list to permit specific
devices in the topology.
So for this vlog, all I'll do is remove the access class.
So show run, pipe begin VTY.
The access class has been removed.
Telnet back,
still not working.
What's the problem?
Notice here, transport input none, so line VTY 04 transport input telnet and perhaps SSH.
Now we've got the same problem we had previously password required, but none set.
So when I type login, we have to specify a password and then we want to specify an enable password
or a secret password.
So now we can login, so we've solved multiple problems in this topology, make sure that you understand
what's required on a VTY line.
As an example on this router, I'll now change it to say, login local rather than just a login
notice
the problem now telnet to
router 2
and notice, I made another mistake, I was actually working on router 1, so you need to be careful
which routers you're working on.
So let's exit out of here.
That's router 1, I'll exit out of here, back on router 2 now, so I'll telnet back to router 1.
It's asking for a username, so I'll try Cisco, password of Cisco.
That's not going to work because I don't have a username configured, so just to reiterate.
On router 1, we used the command log in local.
So this password has no effect.
We have to specify a local user name.
And just to prove the point, I'll say no password Cisco and go back to the VTY.
So there's no password on the VTY line.
I'm back on router 2, Telnet back to router 1 notice it's asking for a username.
The password on the VTY line is irrelevant when you use login local, so CONFT username David Password
Cisco.
I'll login now as David and I can log in.
The reason I can go to privilege mode because we have an enabled password configured on the router.
Notice enabled password, Cisco, we could change that by saying username David,
Privilege and specify 15 to give David full privileges to the router.
Notice the difference now when I telnet to the router and login, I'm taken immediately to privilege
mode and that's because
We specified the privilege of the user as 15.
This is bad practice, you should use a secret.
So there are some troubleshooting tips on how to troubleshoot telnet.
Thank you for watching.
Don't forget to comment on the video or ask questions, please
like the video if you enjoyed it
and please subscribe, I wish you all the very best.