we're back to our lab. First thing we're gonna do is we're gonna sign I P Addresses to Router one interface at 00
Router to interface at 00
Router three Interface, AB 00
and Router four Interface at 00 So that's going to rather one.
And let's look at our interface at 00
interface fast. Internet zero slash zero.
Now, real quick, I'm gonna go back. Why? I'm assigning I p addresses to these four interfaces. Well, because they reside on the same land. You see this land in the middle with the four switches? So, Bo, all four, these routers reside on the same data link on the same land,
we're gonna pick an I p. Address ing scheme to assign to
Roger one router to Router three and router 400
I'm going to use the network 1 51 01 45.0
And the mask I'm gonna pick for 1 51 1 45.0 is a slash 29 mask, which is 255255255 to 48.
Why did that pick us last 29
Because when you write it out in binary with a slash 29 the value of the last bit on is eight. So you get addresses between 80.1, which is about first valid address and 0.6, which is your last valid address 0.7 would be my broadcast
and 0.8 would be where my next network starts.
So since I have four
since I have four routers,
I need four addresses. So it's last 29 is the closest fit. Slashed. 28 would yield me 15 addresses because the value of the last bit turned on its 16 and slashed 30 would yield only two addresses because the value of the last bit on is four. Minus two is two
which last 28. I mean, you get 15 total addresses because the value of the last bit turned on its 16.
So 16 minus two is 14 14 addresses is way too many,
which last 29. The value of the last bit turned on is eight
so minus two. I get six addresses. Yes, I'm wasting, too, because I only need four here, but that's the least amount of waste.
So I'm gonna go back inside rather one
and look at my F zero slash zero interface.
And I see that by default, a router interface is an administratively down mode.
So by default, a router interface is administratively down.
The M two of this interface or the maximum transmission unit, is 1500 bytes and the band with IHS 100 megabits per second or 100,000 kilobits
There's another command you can use to look at all the router into faces at the same time the command is and it is actually one of my bread and butter commands.
This is the command I execute first when I'm solving a problem and I run into,
uh when I run into a problem in my lab or ed work
and the command being show I p
And you see this router has one too.
34 interfaces tour from our Internet interfaces and tour for my cereal interfaces.
I'm just gonna tell you that facet in at 00 and serial 000 r unused other two are just sitting there unconnected to anything.
The I P address is not a sign yet.
and the port is an administrative lied down mode.
to make changes to report a first need to go into that port.
So I'm gonna go into interface Fast Ethernet zero slash zero
And now I'm gonna assign it an I P address.
So since this is a router one, I'm just going to make this 1 51 a 1 45.1
So to assign an i p address the commands in Texas, the word I p
than the word address.
Then if I execute the help feature,
for the i p address, which is
Then once again, if I execute the help feature,
I'm asked for a sub net mask, which is 255255
Unfortunately, and I hit enter for the command to take. Unfortunately, Cisco routers up until now, don't do the slash feature
when you're assigning I piece, it would be nice if we could have just said I p address 1 51 1 45.1 slashed 29. But it just doesn't work that way.
Next. Since the interface by default is an administratively down mode, I'm going to negate the shut down command. So by default,
the port is shut down.
I I'm going to add a no in front off it and hit Enter. And that brings the port up.
At this point, if I look at my show, do show I p interface
Brief command again,
that fast. Internet 00 is up
which is good. You want to see up? Up?
I'm gonna save my work.
I'm gonna use the shortcut command. I'm going to say do right mem or short.
Uh, the short form is Just do right or I can say do w r
Next, I'm gonna go to Router Two and a sign an I P. Address
and router to for some reason, has
Oh, it's configuration missing. I'm going to quickly go ahead and do that. No, I p do mean look up.
Those names are too.
Line console zero logging sink.
Then I'm gonna go into interface fast Internet zero slash zero and assign it an I P address of 1 51 a 1 45 we can pick not to, cause that's within the valid range.
Do I need to exit out of conflict line mode to go into the interface? No, I don't. I can simply type in interface facets in at zero slash zero
kid inner and the prom
pops me over from config line mode to config i f which stands for interface config Inter Face
Gonna sign it an I p address
and then new Shut down the link again. Bring it up.
Look at my do show I P interface Brief command
And I see this interface is up up
this point I saved my work
Router three is again missing. This is weird All its config
So no, I p domain lookout Post name are three line console zero logging sink
Okay, that's takes care for housekeeping can fix next. I'm going to go into the interface fast eating at 00
and given an i p 1 50
i p address, I could simply type i p a d d.
But I don't want to confuse anybody.
and again execute the no shutdown command.
Next, I'm going to see if my work
make sure this doesn't go missing again. And then look at my interface with the Do Show I p I nt brief command
again. It says up, up and I'm happy.
I am going to go to Router four and do the same. Hopefully, writer for hasn't lost and it has lost distant fix. Also, something's going on. You know, I knew Router for has lost its conflicts from yesterday because I already had assigned around her name as our four and I don't see one
so quickly. Do the housekeeping. No, I p domain dash, Look up
then lying Const Well host named host name are four than lying
console zero logging,
and I'm done with my housekeeping. I saved my work.
Next I'm gonna go into interferes faceted as you know zero
and assigned an I P address off 1 51 01 45 dot for so router one is 10.1 router to is not to router three is not three and router forest out for it works.
And the mass to 55255255 to 48.
No, shut my interface to bring it up
and check to see if it really is Up, up. So I say, Do show i p interface brief.
and I see that the interface is up, up and I am happy
I'm going to go test to see if this actually worked. So I'm gonna test connectivity
from router 12 router 23 and four. And I'm going to use the ping utility, which uses the protocol ICMP or Internet Control messaging protocol.
1 50 So I'm sitting on route a one. Remember, guys, I'm sitting on route a one
soaping 1 51 a 1 45.2 which is rather choose a dress
and I had an 80% success rate.
The first ping failed the first i CMB packet sent failed. The next four succeeded.
There's a reason for that.
If I do a second ping to router to all five will succeed and I get 100% success.
I will. Ping Router three now just changed glass octet
up. Arrow key. Bring up The command changed the last October 2.3.
Once again, you will see an 80% success rate. But if I ping it again,
so you see an 80% success rate. Four out of five pings went through. One failed the 1st 1
and a second ping yields 100% success rate. Five auto five pings went through.
Lastly, I'm gonna ping router for
once again, you're going to see an 80% success rate, but a second
set up pings that s and use 100% success rate
Think about why this is happening.
Well, the answer being
the first ping fails because router one is doing the art process.
It doesn't know router to Router three's a router Fours Mac address.
So it cannot build the frame to send over the pink inside of the frame
to router to three or four. So, whence that our process, that request and reply process is happening the first ping times out.
Once that process has happened, Router one has already stored
router 23 and four is Mac address in It's our Table.
So since they're already stored the second time I paying, I get 100% success rate
because Router one already knows the destination Max and can immediately go ahead and build the frame
to encapsulate the ICMP. Pack it in.
So let's look at our our cash or our table with command Show I. P. Ark
and you see router to address is 1 51 1 45 That, too.
This is its hardware address or it's Mac address and it's been in this table for two minutes.
This is rather threes. I p. Address $45 3
and this highlighted portion is Router three's Mac address, and it's been in the our cash or our table for one minute.
This is rather fours address 1 51 a 1 45.4
and this is its Mac address
with it, with the Mac address being in the O. R. Table for one minute.
Now you don't see an age attached to Router one's own I, P and Mac binding
because my Mac address won't
the our table. It can never age out. If I for some reason wanted to clear my our cash, I could execute the command. Clear.
Okay, so maybe it is clear are clear. I pr works
on some router routers. You'll notice as you progress in your network engineering career. Sometimes there are minor differences between the oasis. So one router might have one command, and then you it won't work on another router. And you hit the question Mark Command
to figure out what the proper command is.
So I could clear out my arm cash if I wanted to.
And it really didn't work
on Ah, packet tracer. But the clear our cash command will clear out your arm if you needed to for any reason.
Now, let's make sure the 00 d zero d three b 64 b 01 is actually Router two's Mac address.
Well, let's find out. I will minimize this
and go to outer, too.
And look at the interface in detail. I say show
interfaces fast. Internet zero slash zero
the Mac address off. This interface is 00 D's. You know d three B six, b four, b 01 with matches. What is N Router ones are cash
Now what if I asked you guys So we've looked at the our table. We know how the art process happened. You know how ping happens.
i si m p being the protocol that
the debo command. What it does is takes the internal processing off a router and puts it on screen. A big no, no. In production, you do not use the D book command in production, you can be fired for issuing a debo command at work or in production.
So this is only used for learning purposes.
So if I say debug, i p i c m p
So now let's send a ping from router 12 router for
paying 1 51 0 on $45 for
you See that I sent five icmp messages
it says echo reply received because router one sent an echo packet over to Router four. It was received from the source Router four, and the destination was us. So this was the echo reply that was received from Router four. If you go to outer four and check
writer four, we'll say
I sent an echo. Reply
1 51 1 45 not four, which is its own address and the destination waas 40.1.
Let's turn off the bugging you. Which stands for Lundy, Bug and all on debug All I could have possibly said, I'll do it a different way on Router one. I could have possibly also said
no debug FBI, CMP except useless All assume so
Now I'm going to say debug I p packet
and also on Router four. I'm going to say GI bug I p.
Please Remember, guys do not ever use the Debo command in production. At work, you can be fired. It's a fireable offense because there's so much traffic flowing through a router at a given time. If you said the book, I'd be packing, your screen will freeze and the router me crash
trying to put all that traffic on screen for you
It is very process intensive. So do not do this command at work. I cannot stress enough
anyhow. Now I send a ping from router four. I mean, rather one back to outer four.
So I'm pretty sure I have it in my command. History used up arrow key to pull it up,
and I send the pink.
So let's look at one of the things that I said because I sent five.
The source address was 1 51 a 1 45.1 which is my local address on Router one.
The destination de for destination address was 1 51 1 45 That four.
And it was routed. Wire the routing table.
This we will see tomorrow what this means
right now. This is not supposed to make sense to you.
Then you received a package back, which is the echo reply coming back from router for 1 51 1 $45 for
and the destination off That packet was 1 51 a 1 45 Not one which is you or rather one.
You should have also seen a similar occurrence on Router four.
Let's look at this one right here.
You see that? The source address with the inbound packet was 1 51 1 45.1 and the destination was your own router, which is router for the one we're sitting on right now.
And then I sent a message back, which was my echo reply.
source Address 1 51 1 45.1
No source Address 1 51 1 45.4 And the destination was 1 51 1 45.1 This was my echo reply packet.
And this was the echo that I received from Router one.
I'm gonna turn off debugging
do one more thing and then commence for the day.
You space all to turn off debugging.
Now if I asked you guys a question I want you do 10 test connectivity
from router 12 router. 23 and four in one command. How would you do it?
for the 1 51 01 45 zeros. Last 29 Network 1 51 a 1 45.7 is my broadcast address. Let's see what happens when napping That address
this pink should go out to everybody.
And it does. It goes out to 23 and 45 times and 23 whips, too.
Groups 23 and four. Reply back five times.
Gonna turn off, keep bugging
and save my work. And this concludes this part of the lecture. Thank you.