In previous videos, we configured this topology, we configured an HCP router, we configured spanning
three, we configured IGP on the core switches and this Internet facing router and we've done various
things to optimize the topology.
In this video, I'm going to configure network address translation on router three to enable devices
in our genius three topology to access the internet.
He says rather three, rather three is configured with an IP address on Fast Ethernet zero one and the
IP address is 1921681 124.
Router three has a default gateway of 1921681254.
This is the internet facing router in the cloud.
That router does not have the ability to run routing protocols, so I can't advertise the Ten Network
running within Janus three to that router.
So to get this to work, I'm simply going to enable Nat on router three with this being the outside
interface and this being the inside interface.
Now to be correct with wording, we actually enabling port address translation so that multiple devices
in our topology can be netted to the IP address on this interface.
So on Fost Ethernet zero one, I'm going to use the command IP Nat outside to enable Nat on this interface
and make it be the outside interface.
From a NAT point of view that takes a while to come up.
In June is three, but after a while I should be able to configure this interface as the inside.
And there you go so fast.
Ethernet zero zero IP Nat Insight.
So we've told the router that this interfaces the outside interface and this interface is the inside
interface.
So now we need to configure Nat and we do that by tapping the command ip nat.
Inside.
I want to net devices on the inside network.
And in this case, I want to net source IP addresses based on an access list, which is going to be
access list one.
And we're going to net them onto Interface Fost Ethernet zero one and we're going to enable Pat by using
the overload keyword.
So the next step is to create an access list, which is access list one referenced over here in the
net command.
And I'm going to permit all devices in the Ten Network.
So show run pipe include Nat.
Shows me that we've got Nat configured on the inside interface.
Nat is configured on the outside interface and we overloading the outside interface.
Now, to be precise, we should do this show Run Interface, Fast Ethernet zero zero and we can see
that IP Nat inside is enabled on that interface and IP Nat outside is enabled on Fost Ethernet zero
one show IP Nat translations.
At the moment there are no NAT translations, so let's go on to router one acting as PC one.
And let's see if we can ping google.com.
At the moment.
Notice, please, that it's trying to translate google.com using a broadcast.
And this takes a while to time out.
The reason why is.
The radar is doing a domain lookup now that's not shown by default in the running config, but if I
type no IP domain lookup and then try and ping google.com again.
Notice the ping times out immediately.
So if I use IP domain lookup.
I should specify my DNS server.
So IP name server.
And in this case, I'll specify Google.
When I try and ping google.com in this case, notice it works.
We got a reply from the Google DNS server and we were able to ping google.com.
Rata once traffic is being netted by router three.
So notice we can see the net translations.
Yes.
The connection to the Google DNS server.
And he has the connection to Google.
This is the IP address of router one on the inside interface and this is the netted IP address of router
one, which is the IP address of fast Ethernet zero one as shown over there.
I'll show these together.
So debug IP Nat.
And that's actually on the wrong router.
So on all router three debug IP net and what I'll do now is I will do a ping to Google.com and what
we should see is we should see the net translations taking place and there you go.
Notice Source IP address ten one 1011.
This IP address was translated to 1921681 124.
That's the IP address once again of Fost Ethernet zero one on router three.
Going to Google.com.
The initial ping timed out.
So we saw that there.
But there's the second ping and there's a reply to the ping from Google destination IP address of 121681
124 is translated back to 10.1 10.11 is forwarded through the network to router one show IP net translation
shows me that at the moment there are no net translations they've timed out.
So let's telnet to google.com on port 80.
You can see that it's connected.
So it's opening that connection and in the net translations you can see here's the DNS request to the
DNS server and the reply and he has the connection to the Google server to show IP net translation shows
me the DNS request and this is the connection to the web server.
In other words, google.com on Port Eddie we can see that we are currently connected to the Google server.
I'll press control C on the router press enter.
We can see something happening in the natural translations.
I use control shift six x to jump back to the router because it's keeping the connection open.
So I'll disconnect my connection.
So we've successfully configured Nat in this network, allowing writer one to connect to Google.
Let's do the same on router two acting as PC two.
So on PC two, IP name server will be google ping and let's use another server cisco dot com.
Can see that the query succeeded and we able to ping Cisco dot com what about CNN dot com.
In this case, the pings are being dropped by the server.
So let's try Yahoo!
Dot com.
We can see that the pings succeed.
So we've successfully configured this entire network as well as configured Nat on router three and these
routers acting as PCs can now access devices on the Internet.