One of the great things about history is you can have many devices as part of a typology and you can
access the consuls of every device.
So as an example Rodda one and Rodda too can be accessed directly through Janissary on my local PC.
However in the real world you probably going to want to telnet to devices because you don't want to
walk to the device and connect to the console.
That's not realistic.
If the devices are on the other side of the country or other side of the world so you're going to want
to use a protocol such as telnet to gain access to the remote devices.
Let's assume that router one is in one part of the network and brought it to is in a different part
of the network.
In this example all telnet from a one to router 2 let's see what happens by default.
So telnet to 10 or 20 I'm told that password is required but none is set.
In most cases by default you cannot telnet to a router you have to do some configuration to allow telnet
sessions and to top quality the line Viti Y and specify a Viti y range from zero to a number that depends
on the device.
So in this Rodda the Viti y ranges from 0 to nine hundred and three which means you could have 904 simultaneous
virtual terminal lines or why lines on the router.
In other words 904 sessions could be made to the Rodda at the same time.
You'll often see in documentation that they'll create the Y lines 0 to 4 which gives you 5 D-y lines.
That's something from the old days.
But a lot of Cecka devices today support many more lines than that.
So as an example on the switch Viti Why 0 notice there's 5400 VQ lines on this virtual Iowa's vilayet
to switch.
And if I connect to this physical 30 750 and top line Viti Why is 0.
Notice this one has 16 Viti white lines.
So that really depends on the device.
This ios VLA to switch has one thousand and one D-y Why lines.
I'm going to specify log in and notice I'm told that to log in is disabled until the password is sent.
So once again if I telnet to the Rodda the telnet session is closed.
So I wrote it to let's add a password of Cisco and now try telling it to the Rodda notice I'm prompted
for a password.
I want to enable I'm allowed in because this router has an enabled password but if no enable password
was set so let's disconnect if no enabled password was set.
No secret password was set.
Notice what happens telnet to the router and to my telnet password top enable and I cannot get to enable
mode because no password is configured.
You must configure either and enable password or a secret password secret being better to go to enable
mode through a telnet or S-sh session.
So I noticed the configuration that we did show run pipe begin V-twin in this case we enabled 5 Vicci
y lines 0 to 4.
Were using a password on the line for those five lines the same password is used for all of them.
You could specify different passwords for different Viti white lines if you wanted to.
But in this example we'll keep the password the same.
Hence when I tell that from router 1 to 2 I need to put in the password on the line but to go to enable
mode I need to type the Enable secret password.
Now again on the Viti y line similar to the console we could use the option log in a local which would
use a local username and password database telnet back again.
It just now asked for the username and password of the user but in this case its failing.
So let's see what's going on.
Show run pipes include user no user account configure it.
So hence the authentication was failing.
So I need to type user name whatever the username is and the password of that user.
So now I can log in and then type and able to get a privileged mode.
So once again what do we do we created a user called davit with a relevant password.
Not a good idea to use passwords such as the following.
You should use secret.
So I should have done this.
Use the name David.
Secret Cisco.
Now I'm told I cannot have both a user password and a user secret.
Choose one or the other so do show run piping clewed user.
Notice the use and you still using a password rather than a secret.
So let's say No user name David and recreated with a secret and that's allowed now.
Now it is previously the password was in clear text dush run pipe.
Include user the user name is now an empty five hash.
So it's much more secure.
Notice the difference now however when I tell them that and put my username in and my password I still
have to put in my enable password.
But that's a secret password.
And what I can do additionally specify privilege and give David full privileges rather than the use
of having to type the enabled password or secret password in this case.
So back then write a one tell it to write a T name is David falshood a Cisco notice I'm taken immediately
to privilege mode whereas previously I had to type enable and then put in the secret password.
Now the biggest problem with Telnet is it's clear text so legs it back to route 1.
Let's start doing a capture whya and capture the traffic received on this interface.
I remember we created a secret password.
So on the router show run doesn't show us what that uses password is what happens when we telnet however
said telnet whose name is David.
Password is Cisco straight to privilege mode.
Well search for telnet and let's look through the packets first.
Strolling along there is D A V I D asking for password.
Now see I see we've just captured the user's password.
If we follow the TZP stream I'll just copy that into notepad so you can see it clearly.
But what you're seeing here is the TCAP stream showing the user name and the password.
So the password is shown in clear text tellen allows you to capture passwords and other data off the
wire.
So it's not a great idea to use telnet.
You may think it's good to use a secret password but be careful the secret password is hashed on the
router.
But when the data is sent across the wire it's in clear text.
So a hacker can capture the password so you should be using S-sh rather than telnet before each before
showing S-sh.
One last thing on telnet you can also set an exact timeout on your telnet sessions so that they get
disconnected.
If there's no activity for period of time in this example after five minutes the telnet session would
be disconnected but you could specify another value if you wanted to.