Time
15 hours 34 minutes
Difficulty
Intermediate
CEU/CPE
16

Video Description

Point-to-Point Protocol Lab For our PPP lab, we're going to demonstrate how to set up for PPP link testing, why /30is supposed to be used on PPP links, and how to confirm connections between the simulation targets then what happens before and after when we change the encapsulation type to PPP. From this lab you'll also learn options for executing the Encapsulation command, why layer 1 stays up and layer 2 stays down, what you need to do to enable UP status on both targets, and why there is a host neighbor router installed to the routing table & how it gets there.

Video Transcription

00:04
All right,
00:05
folks, I have configured or I have created a very simple topology. You have rather one connected on s 000
00:13
to router to as 000
00:16
The I P addresses on these interfaces are
00:20
If I say do show i p interface grief.
00:25
Router one has an I p. Address of 201 11
00:30
and router to has an i p. Address off.
00:35
Unfortunately, I've named this router one also. Let's change the name to our two.
00:41
So router to has an I p address of
00:46
201 12
00:50
If you look at the interface itself under my running config,
00:55
you see that I've assigned the mask of 2 52 to 55255255252
01:00
or slashed 30 which is supposed to be used on point to point links.
01:07
If I look at my interfaces show i n t
01:11
as 000
01:15
first thing, you will see that serial 000 is up and line protocol is up and it's connected.
01:23
And you also see that the default encapsulation type on my cereal interfaces high level data link, clear control or h D l C.
01:33
Let's try and bring across from matter 12 router to and make sure absolutely sure that we can connect. We can ping.
01:41
So I'm sitting on rather one
01:44
I'm gonna paying 201 12 and we are pinging.
01:49
Now let's go ahead and see what happens when I changed encapsulation type
01:55
to P P P.
01:57
Now, Before I do that, let me show you the routing table over outer one
02:00
show I p route
02:04
Do show I P route.
02:08
Now you see, the only the only connection or the only row showing up
02:14
on Router one is my 201 10 network, which is directly connected to serial zero, and rather too, would show the same.
02:23
Now, let's go ahead and change the encapsulation type
02:30
to P p. Pee with command encapsulation. We do a question mark. Three options. We have seen its TLC.
02:38
We're going to try and attempt to change the PPP
02:43
and then later on will discover and explore for him. Really?
02:49
So encapsulation PPP enter
02:52
and I got a message saying that line protocol on interface yield 000 has changed too Down
02:59
we look at our interface brief.
03:01
You see that the line protocol stays down, status stays up. So lair one stays up, but later to stays down.
03:12
The reason being that at the other end of the link on router to we still have not changed. Encapsulation two ppp
03:19
so router to being HDL see on serial 000 and rather one being PPP
03:24
on serial 000 creates a mismatch encapsulation type on the two ends
03:30
which takes the link to up down
03:34
If we go ahead and go into serial 000 on Router two and change the encapsulation to P P pee, you immediately see that the line protocol on interface 000 has gone to up.
03:47
If I look at my interface brief
03:53
Do show i p i n t brief
03:57
and you see that we are up up now
04:00
by paying to the other side
04:03
201 11 me right now being on router to So I'm gonna ping rather one
04:10
and it works.
04:13
Now let's go take a second look at our I p routing table on route or one.
04:18
So if I execute the command, do show i p route
04:29
we see a secondary route that has been sold
04:33
in our routing table.
04:35
Now PPP automatically installs Ah, host route. And if you remember, our host route is a route with a slash 32 masks
04:44
to the opposite end of the link.
04:46
This is called a pair neighbor out and this is a function of P p. P.
04:51
This got automatic me installed in our routing table. Once we changed the encapsulation two PPP,
04:58
this is default PPP behavior. So I have a direct route
05:02
to the 201 1 to address on Router One. And if I check on router to you will see a direct route to the 201 11 address
05:14
on router chew with this last 30 to mask. And here it is.
05:18
Once again, this is called appear neighbor out and this is default PPP behavior.
05:27
Next,
05:28
remember I said that PPP can perform authentication
05:31
between two devices so that each device can authenticate the other and make sure that the device talking to us is who they say they are.
05:42
Well, there are two protocols that PPP uses. Fourth indication,
05:46
1st 1
05:48
we're going to cover is password authentication protocol
05:53
So if I execute the command
05:56
p p p
05:58
authentication
06:00
and execute the help feature, you see that they are two protocols
06:03
that control authentication over PPP links or point to point protocol links.
06:11
The 1st 1 we're gonna cover is Pat
06:14
Pap sends the password or the over the link in clear text,
06:18
which is not good.
06:19
However, it is part of our c, c and s. So we're gonna cover it anyways.
06:24
Now, what is going to happen is one side
06:28
off the link router one is going to be the authenticator,
06:32
and the other side router to is going to be the attentive Katie.
06:40
So if your outer one is going to be the authenticator
06:43
first we need to have a date. Abi's against which router one can authenticate route or two.
06:50
We create this database locally
06:54
by executing the command
06:56
user name and then the host name off our two router to which is
07:01
lower case our troops.
07:04
So I simply typing are too.
07:06
And then with a question mark command, I see this option password.
07:13
So I'm going to create a password that router to must match with rather oneto authenticate itself
07:18
password. We're gonna leave the password as or create a password saying Cisco to the password being Cisco.
07:27
Next, I'm going to log into the interface or going to interface serial 000 off rather one. And tell Roger one that it is going to be the authenticator by executing the PPP
07:40
or 10 *** eight.
07:42
And then since we're doing pap or password authentication protocol, remember,
07:47
password authentication protocol sends the password over the link in clear text.
07:53
Now, Router one is trying to authenticate router to
08:00
at this point, if I look at my link
08:05
with the show I P interface brief command,
08:09
you will see that the link has gone up down.
08:11
If I g bug PPP,
08:16
what indication
08:20
and debug PPP
08:24
negotiation
08:28
and debug PPP packets.
08:33
You will see the PPP is sending back package back and forth or trying to at least authenticated router one. But at this point,
08:41
PPP is unable to attend to Kate.
08:46
Rather, one is unable to attend decayed router to sew. The link has not gone up yet.
08:54
As you see, the link control protocol state is open, but the link is still down.
09:01
If we go on router to the authentic 80
09:13
and go into interface 000 which is connected to a router one
09:20
and say PPP
09:22
authentication or PPP Actually PPP
09:28
pap, since we're using pap
09:31
or password authentication protocol,
09:33
then sent user name.
09:37
And the username we're sending is our hosting,
09:41
aren't you?
09:43
Then the password, the password that we send here and the user name that we sent here must match the database that we created on Router One. Namely,
09:54
we go to rather one
10:01
and I look in my running config
10:11
If you look I created a user name for our our router to as our two and the password Cisco.
10:18
When rather too tries to attend Tecate itself with rather one this host name and this password must match
10:26
to what rather one has in its database. The database for us is just one line. This could be many more lines if there were other outers.
10:35
So we go back into a round or two.
10:37
Well, let me go ahead and turn the authentication on. I mean debugging on another one. So we see something debug PPP
10:46
indication and debug PPP events,
10:50
PPP negotiation
10:58
Go tour outer too
10:58
and we say ppb Paps and use the name are two password
11:05
Cisco.
11:07
At this point, the link you see came up
11:11
and on Router one.
11:16
You see
11:18
that router one finally got the user name
11:22
are two and pass Francisco from Router to and it attended gated route or two.
11:28
And you established your connection.
11:33
You finish the LCP phase and the connection is up
11:37
and
11:37
the interface came up.
11:43
If you if I look at my show, I'd be into face brief command again. You will see
11:48
that
11:50
mind two faces up and up and I should be able to paying 201 1 to that being rather too.
12:03
Next, we're going to explore chap.

Up Next

Cisco CCNA

Our free, online, self-paced CCNA training teaches students to install, configure, troubleshoot and operate LAN, WAN and dial access services for medium-sized networks. You'll also learn how to describe the operation of data networks.

Instructed By

Instructor Profile Image
Junaid Memon
Instructor