Okay. So, as you see, this is the same topology we have been using throughout our labs and same topology. I drew on the board without switch. 123 and four present.
Roger. 21 is going to try and route to these two sub interfaces on router. To
which are if I execute the show, I be interphase. Brief command
are the 10 dot Tenn dot Tenn dot to 54 $20. $20.20 dollars to 54 addresses.
Now, if we go to router to a one
maximize and check our routing table show I p
you see that the only network available to router to a one at this point is the 200 network, the 202 102 100.0 slash 30 network.
And it says Little C
say it means that this network is directly connected.
The legend on top also say C stands for connected.
to $10.10 dollars, 10 to 54
Break out of the ping by executing control shift six. That's the brake sequence. I didn't want to wait for five things to fail
I p. Packet. And remember, the Debo command puts the internal processing off a router on screen for you to view
not to be done in production. Once again. Do not do these commands in production.
And if I ping again,
Let me break out with control shift six.
It says unr out herbal.
I turned off my debugging.
to do is put routes in my routing table.
Put routes for the 10 and the 20 Network on my routing table. The 10 and 20 network have a slash 24 mask. Let's make sure
if I say show I p interface
which is different from the show Interface Command. Previously, when I was doing the command show interface facet in it
gino slash 1.10 without the keyword i p it was showing me a physical
characteristics off that interface. Now it's gonna present to me I'd be related information
since I added the keyword. I pee into the command
intervest faceted as you know slash 1.10 has an address of 10 9 10 9 $10 to 54 with this last 24 Mass, which is 2552552550
Let's look at interface Fascinating. It's Euros last 20.
I pull up the command using the up arrow key,
so I'm gonna execute the show I p interface. Faceted as you know, slash one doc 20
the address is $20.20 dollars, $20 to 54 with a slash 24 mask.
So let's go back to router to a one.
And let's create two routes to the 10 and 20 network,
My destination network is 10 dot Tenn dot Tenn 10.0.0.0.
My mask is 255255255.0.
I can either specify the next top I p address
or in this case, this guy stays over here on the C l I. It says fording routers address, which would be
the address of the next top. Routers were asked. Traffic leaves
my router One. What is the i p it encounters along this path
the next i p. It encounters is the cereal 000 i p. Address on Router one, which is
show I p interface brief,
which is 202 102 100.1 on serial 000
I'm going to not use the next top I pee. My other option is to simply use an exit interface.
So our exit into face in this case is a serial interface.
The serials, you know, 10 interface on router to one which faces rather one.
And then I may specify an administrative distance.
Right now, the default administrative distance. Remember the administrative distance being the trustworthiness off a routing protocol?
The default administrative distance for a static is one. So I'm just not going to say anything. I'm just gonna press one. Or I could just leave this blank and hit Enter or I could add one hair
and hit. Enter. Now I'm going to create
with the I p route. $20.20 dollars, $20. 255255255.0
the rule of thumb is
or a good rule to follow is that you always create routes,
pointing out an exit interface when you're over a point to point link.
The reason for that is beyond the scoop of the C, C and A class. It is actually
closer to D. C, N P and C C I level stuff.
So I'm not gonna do an explanation off why you should create
a static route pointing out an exit interface on a serial on a point to point serial link. Just remember that rule and always follow it.
So when pointing routes out of a point to point link or out of a serial interface, you always use the exit interface I D. Which in this case is cereal 010
I have created the to route to Metro 10 and Network 20. Let's look at these routes in our routing table.
Well, actually, what I'm going to do is bring up
the static route that I created for the 20 Network and changed the administrative distance to eight.
So the next field is the administrative distance field. Say is distance metric for this route,
I'm gonna change it to eight.
Now looks, look, ads are running config Sure
and let's find the static routes by scrolling down.
now a few things about administrative distance.
One. The default administrative distance
You don't see anything here.
That means this has a default administrative distance and the distance being one.
Cisco routers or Cisco devices often do not show defaults in the running conflict, so you will not see it one. However, you should know when you don't see anything here that this route has a default administrative distance.
However, since I changed the administrative distance for the 20 Route
28 and it is not the default it shows in my running conflict,
administrative distances can vary between zero and 255
So connected route. The original routes that we had in our routing table. If I say a show, I'd be route connected.
This is what we show saw originally, the 200 network, which is connected.
This connected network has an administrative distance or connected route, has an administrative distance off zero
static route by default, have an administrative distance off one
for the second route to the 20 network. I changed the administrative distance to eight. Hence his shows. It does not show on the first route because it is default and Cisco routers and other devices. Switches do not show defaults,
so administrative distances can vary between zero and 255 Remember that
route with administrative distances off? 255 are not installed in the routing table.
Now let's look at our static rounds in the routing table. Show I P route
or I could even say, Sure, I peer out static, but let's look at the whole routing table first. So at the bottom, hair is are connected route,
which was a 200 network which was directly connected on serial 010
Now you see something interesting.
Network 20. Well, first
you see that the little s on the left hand side,
it stands for static. So these two routes are static grounds.
Now you see something interesting. Network 10
and network 20. Sure as directly connected.
Whenever you point a route out
a direct, whenever you point a route out, often interface instead of using the next top option, that route shows up as directly connected
on a point to point link. You should always do this, and it is a good rule to follow
now, since this route shows that directly connected does this administrative distance becomes zero or it remains at
The answer is that it remains at one. That's a trick question that is sometimes asked on the exam.
Just because it shows up as directly connected doesn't mean the default administrative distance changed to zero. No, it is still one.
Now let's try and ping to these
to these networks. Let's try paying the 10 dot tend not tend to 54 address, which exists on router to. So I'm trying to go from not or to a one
two here, two router to to the two addresses that exist on this interface.
Let's try that ping 10 10 $10 to 54
which is destination unreachable.
It is also an ICMP type message. It is an ICMP message,
Internet control messaging protocol message and the router. Somebody is telling me that this destination is unreachable to you.
Let's go turn on debugging on Router one and router to a one,
I well Let's just look at the I c m p d. Book First,
I'm going to ping from router to a one.
I'm gonna turn on my I p packet debugging debug I p packet
And then I'm gonna attempt to ping again.
I'm getting a message
that says Routed y Our rib
rib stands for routing table or route information base.
the routing table, the word i p routing table and the word rib or route information base are synonymous. It's one of the same thing. So it's basically telling me I routed the packet out.
Let's see what happens at Router one
router one is sending me back a destination, unreachable message or a host. Unreachable message.
The host unreachable destination was $10.10 dollars, $10 to 54 but
router one sent back.
Ah, host unreachable message back to router to a one.
let me turn off the ICMP debugging and said the bug
i p. Hackett and then try and ping again from router to a one.
Let's see what happens on Rather one. Now
Router One now is saying that this message is unraveled Herbal,
for when router to a one cent. The traffic out the ping traffic out router of one receives it.
However, if you check router ones routing table, you're trying to get to network 10 dot Tenn dot Tenn 10.0.0.0 slash
If I look at rounder ones routing table,
I see that router one is unaware of the 10 Network. So of course it drops the traffic and sense router to one. A message back saying
This destination is unreachable to me.
So we need to add two routes
to Metro 10 and Metro 20 also on router one.
So I'm going to say I be route
Tenn dot Tenn dot Tenn 0.0.0.0 is just my destination network, then the destination mask.
instead of picking and interface to rout out off,
I am going to give it the next hop I p address
a good rule of thumb again. Another rule is when you're creating routes that will
a multi access interface, a monthly access into Frisbee ing eternity or, in this case, fast Internet.
You always always use the next hop routers I p address, not the exit interface.
traffic flowing in this direction the next I P address I encounter is router twos as zero slash zero interface address,
which is Let's check
show I P interface Brief
router twos at zero slash zero interface addresses 1 51 a 1 $45 too.
So that's what I'm going to use on Router one as my next stop
So I'm simply going to say
The administrative distance for this route remains one,
and I also need to create a route to my 20 network i p Route $20.20 dollars, 20.0
for a slash 24 mask and the next top I'd be remains the same.
However, I'm going to change the administrative distance here to eight Also just assure you the difference.
I look at my routes in my routing table,
or to get a cleaner output, since these two
are connected routes. The 200 network facing router to a one and the 1 51 1 45 network facing Router
23 and four. I want to leave this out for a cleaner output? I can actually say Sure I p route static
and just get my static routes. Now, I have a route to the $10.10 dollars $10.0 network
the next top I P, which is 1 51 a 1 $45 to. So I will be sending my information to this I p, which is round or two
now. This first field
in the middle of this output. This first field in the bracket
is your administrative distance.
You see, it is one for the default that we didn't change an eight
for the 20 route, which we change to eight.
Okay, once again, if I say sure running config and look at these routes in my running config,
the route with the default administrative distance of one does not show
the route with the non default administrative distance of eight shows the administrative distance because Cisco devices do not show defaults
now will it work? Let's find out.
I'm going to turn off all possible debugging
not paying 10 dot n not end up to 54
and it's still not pinging.
So let's say debug I p I C M p
and Try and Ping again
and I don't see anything.
Well, let's do a trace route.
Trace out is a function
where you can get the eyepiece between one source and one destination by doing a trace route to it.
every router that the trace passes through will send you back its I p address. So you will know how far you got before a problem occurred.
So I do a trace route to 10 not 10 not $10 to 54
a message from outer one.
And then it's not going beyond Router one.
So let's go to one. Let's go to closer to the source of the problem
and figure out what's wrong.
i p I c M p in a trying ping, Tenn dot Tenn dot end up to 54 again,
and I am getting an echo reply
So what's going on here?
let's go to Router, to
which is closer, even closer to the source of the problem. Who's router? One is standing traffic to router to just fine
screwed around her to and say
and then send a ping from Router two. A 12 router to
on drought or choose 10. Not 10 not 10. Not 2 54 address, which is on fast Ethan It judo slash 1.10
router to is trying to send a message back, but it says unr out. Herbal unravel to destination. 202 102 100 too well, of course,
a ping consists often echo and an echo reply. We created routes and router to a one.
We created routes and rather to a one to send the to send the traffic to outer one.
We created routes on Router one to send the traffic all the way to router to, but router to does not know how to get to this 200 network between router to one and rather one.
If we look and a router to his routing table,
you see that router to does not have the 200 network in its routing table on Lee, the 10 Network, which is connected the 20 network, which is connected, and the 1 51 a 1 45 network, which is also connected.
We need a route. I peer out
to the 202 102 100 0 network between
Router one and Router to one.
The mask for that network is a slashed 30 Mass, since it's a point to Point Link is 255255255252
And then once again.
Since this route is going to point out a fast Internet interface, which is a multi access link, multi access standing for more than two people can be on the network at the same time. In this case, it's rather 1234 So that makes four hosts on the network at the same time.
So I'm going to look for a next hop i p.
So traffic going this way back to Router one encounter the first I P then it will encounter is rather one F zero zero's interface address, which is
So now I have a route back to router
the network on which router tool one sits,
and this should now work.
So let's go to Router to one and ping the 10 10 10 to 54 address. And of course it works. If I do a trace route
Tenn dot Tenn dot to 54 address,
you see that you passed through outer one and then you reach route or two. Now,
at this point can router to a one
Ping 1 51 a 1 45 got three, which is the fastest in at 00 Interface address on Router three
is the address of this interface right here.
So this network whole whole network here is 1 51 a 1 45.0 slash 29 Roger one is 10.1 Roger to his dot to rob her 3.3 and rotter Ford's 0.4 just to reiterate.
So if I try and Ping Router three. What happens?
once again if I check my routing table,
you see that the 1 51 01 $45.0 network is not in my routing table. Hence I cannot ping router three.
Now, what if I told you
I only want you to be able to paying Router three
not router to not router for only router three.
if I created this route,
I peer out 1 51 a 1 45.0
255255255 to 48 for the slash 29 mask and then the exit interface, which is cereal 010
So once I have created this route on router to a one,
I'm going to try and paying Router
1234 on the 1 50 network.
So the each routers fast, Ethan at 00 interface. So I'm going to execute the Ping Command from conflict mode by putting the word do infront duping 1 51 01 45 dot walk
and I can Ping Router one. Why? Let's go Look at Router one.
router. One knows about the 1 51 on one network,
the return traffic to the 200 network can be sent because the 200 network is directly connected to a router. One.
Let's go ahead and paying router to from writer to one Now up Arrow key to bring back the command changed the last out tattoo too.
And Router two is also reachable. Once again,
we go to router to and check the routing table
and I say, Sure, I'd be route
and you see that previously I already created a static route. We did it about five minutes ago back to the 200 network. So router to exist on the 1 50 network
because it is directly connected and the return traffic for the echo reply can be sent back because router to knows aboutthe 1 50 network.
Now, if I try and paying Router three
and router for you noticed, it does not work.
if I go to Router three
and check the routing table
Router three does not have a route back to the 200 network.
I p tack it on Router three
and resend the ping from router to a one
check on router three.
So if I rescind the traffic from router to a one true router three. I'm sending it to Router four by mistake
and check on Router three.
under my debug I p packet. This is unraveled Herbal.
So I turned off my debugging
and I need a route back to the 200 network.
So let's go ahead and create that route back to the 200 Network. I've the route
255.255 dot 255.252 Because that point to point link between rather one and 21 has a slash 30 mask.
my traffic from Rather three is going to be leaving
a fascinating and interface. So going back, I need the next top I p, not the exit interface.
So traffic going back this way, we'll encounter the first I paedo encounter is the i p off rather 100
I'm going to create the same route on router force at the weekend Ping router for also, since Router four also does not have a return route
to the 200 network, simply going to copy
that route off of route or three.
Look at my routing table to make sure just assure you that that route does not exist in the routing table. They're out to Network 202. Rather, four will not be able to send traffic back to router to a one
and paste that route and hit. Enter
from router to one, I should be able to paying Router three and writer for Also
it's a router. Three. It pings and writer for it pings.
However, I'm going to go ahead and remove that route
to the 1 50 network. I peer out 1 51 01 45.0 route
two networks. 1 50 that enabled us to ping router 1234 On the fast Internet interfaces. I'm gonna delete that route.
So I simply put a new in front of the whole command. And that takes away that route.
What if I asked you?
I want a route that only pings router three
not router to not router for
but on Lee Ping's router three.
If I created this route,
this route is for the whole network. If I created this whole route, you would be able to ping router one router to router three and router. For
what If I only want to be able to ping
Router three. Well, there is a way
Not one. No one got 45. Now, instead of using a network address of 450.0,
I create the route to router threes. I p address on fast Ethan at 00
So that is 1 51 01 45.3
I use the mask off all to five fives and a pointed out off serial 010
This type of route to a single address with an all 255 mask is called ah host route because it is to a single host.
I checked my routing table. You show I peer out
and I see my 1 51 01
$45 3 route has a slash 32 masks.
So can I. Ping Router three duping 1 51 01 $45 3
Yes, I can. Kidnapping router to
Cannot paying router four.
kidnapping router one.
No, not on the 1 50 link.
if I'm trying to ping this link,
which is on the 1 50 network
router to one cannot get to that either. Even the router one is directly connected because the route for this
this link does not exist in the routing table.
Now let's go to Router four
and take away our round back to the 200 Network.
that Router four is a router for some company and router one is there I S P router or Internet service provider router.
Now, if you sat on Router four and try to create routes to all destinations on the Internet one by one,
it wouldn't be a good idea
because there are millions of destinations
on on the Internet. So if you wanted to create static routes through all those destinations, you would be here forever.
Router four can create what is called the gateway off last resort
or the default route.
So to create a default route, I say I'd be route,
and then I'm going to say for any destination.
the I P address that I'm going to use It's not the 200 network
a route to all destinations so any or all destinations I can substitute that with 0.0 dot zero with the mask 0.0 dot zero about zero pointing to router one.
that I have created the
default route on Router four, pointing to my SP, which is rather one, I look at it in my routing table. Do show I p route and you see
this route to the 0000 slash zero network, which means any network
points back to my SP router, which is rather one or 1 51 a 1 45.1 with an administrative distance off one.
The star means Star over here means that this is a candidate default route.
And since we only have one candidate default route, it got picked to be our gateway off last resort.
So this is your static default route
just to test it out.
four out of fours host route for out of fours I p address.
You shouldn't be. Here
it is. I changed it three
to a four, so I'd be Route 1 51 1 45 dot for with the all too five fives
mask pointing out serial 010
I should be able to ping router for because Router four should be able to send me traffic back using that default route.
This concludes our static routing lecture.