In this lab, you need to configure network address, translation or net.
Okay.
So in this lab we've been told to configure the router with dhcp on the internet facing interface.
So on the router I can see that it's just booted up.
So enable first thing I'll do is configure the router with a hostname of let's say write a one per the
diagram interface gigabit 001 IP address and we're going to use DHCP on that interface and I'll know
shut the interface.
So show IP interface brief.
We can see that the interfaces up up.
But no address has been assigned yet.
Notice this link is showing orange, so we may have to wait a while for spending tree to converge.
And there we go.
It's gone green.
In this lab, this DHCP server is allocating addresses to the router, so it may take a while to receive
an IP address.
So while we waiting, I'll configure the inside interface with an IP address of ten 11254 slash 24 and
no, shut the interface.
As you can see here, spanning trees, also converging on the side.
And while that was happening, we've now been allocated an IP address on the gigabyte 001 interface.
So show IP interface brief.
We've got an IP address on the routers internet facing interface.
It was allocated via DHCP.
We've also got an IP address configured on the inside interface.
Can the router ping the DNS server?
Yes, it can.
Can it ping?
Swisscom.
Now I've found with packet trace.
You may have to wait a bit when you do your initial pings, so just be patient and see what it does.
But in this example, I can ping Cisco dot com.
Can I ping facebook.com?
So ping facebook.com.
Yes, I can.
So that's good.
Internet site is working and now we need to configure DHCP on the internal network.
So conf t ip dhcp pool and I'll just call this net network is going to be ten 110 slash 24 mask per
this information default router is going to be ten 11254.
DNS server is going to be Google.
So there we go.
Show run.
That's our DHCP configuration show IP, DHCP pool.
There's the pull information.
We've got IP addresses in this range.
Now the router is using this IP address.
So you don't have to do this for this lab, but in the real world, you're going to want to create an
exclusion range.
So let's exclude IP addresses, say, in this range.
Now remember again, these are challenge labs.
Hopefully you've learned something by watching this video.
If you didn't configure an exclusion range, be careful.
In the real world, you probably want to do that in the exam.
They'll be more specific about what you need to do.
We don't want the Rada allocating its own IP address via DHCP.
That does sometimes happen.
So again, show IP DHCP pool.
The pull range is this, but we've got an exclusion range, so we've excluded the Router's IP address
show IP DHCP binding.
At the moment, no clients have got IP addresses.
So let's go onto one of the clients, go to the desktop, go to command, prompt.
And use the command.
IP config.
No IP addresses allocated.
So let's do a new to force the PC to send out a DHCP request and ask for an IP address.
So there's the IP address.
So can we ping the router?
Yes, we can.
Can we ping the DNS server?
And the answer is no.
And that's because we need to configure network address translation on the router.
So on the router interface gigabit 001 IP, Nat, and this is going to be the outside interface interface
gigabit 000.
This is going to be the inside interface.
So we've configured.
Outside and inside interfaces.
Now we need to use the command IP net and we are netting inside devices based on a source list.
In other words, an access list.
In this example, to keep things simple, I'm going to use access list one.
You could have used a different access list if you wanted to.
Interface is going to be gigabit 001.
And don't forget to add the word overload.
You must overload the interface to enable Pat.
And then the last step is to create an access list where you decide which traffic to permit.
In this example, I'm going to permit any in the real world.
You probably want to limit that.
So don't just permit anything to be netted.
So on the PC now, can we ping the DNS server?
Yes, we can.
So back on the broader show, IP DHCP binding.
This client has been allocated an IP address.
Show IP net translation.
Notice we can see that this client has been netted.
To this IP address, which is the IP address on.
The outside interface.
In other words, the router.
On this interface has been allocated to this IP address via DHCP and the PCs are being netted to that
IP address.
So this PC has been netted to the Router's IP address.
So close the desktop down and open up a web browser.
Can the PC get to Cisco dot com?
Yes, it can.
So Cisco dot com is reachable from the first PC.
What about Facebook dot com?
Facebook is also reachable.
So I'm happy with that.
This PC can access both Cisco and Facebook.
What about the second PC?
So command prompt IP config and no IP address has been allocated.
So what I'm going to do is force the PC to get an IP address through DHCP.
It's now been allocated this IP address.
Can it ping the DNS server?
Yes, it can.
Can it ping Cisco dot com?
Yes, it can.
Can it ping Facebook.com?
Yes, it can.
So I'll go to the web browser.
This PC can access Cisco dot com and it can access Facebook.com.
Let's configure the lost PC.
So desktop command prompt IP config need to get an IP address via DHCP.
So force the PC to request an IP address.
There you go.
So can it ping Cisco dot com?
Yes, it can.
Can it ping facebook.com?
Yes, it can.
And as a last test, I'll open up a web browser.
Facebook.com.
Cisco dot com.
I'm happy with that.
The PCs in the internal network have been allocated IP addresses of via DHCP.
The router has been allocated an IP address of DHCP and the internal PCs can access the internet because
the router is netting the IP addresses.
So show IP net translation.
Here are a whole bunch of net translations.
Notice we've got PCs.
Sending DNS requests to the DNS server support.
53 is DNS and 8.82.8.8 is the DNS server.
We can see a PC.
This is the second PC.
PC one accessing swisscom using HTTP.
So the internal hosts are using random or what are called ephemeral ports, greater than 1023 to access
servers on the internet.
Notice how the inside a local address has a different port number to the inside global address because
we're using pat.
The router needs to differentiate.
Between different translations here they the same.
But notice here we have differences.
The Rada needs to be able to differentiate between different sessions going to the same server.
So here the first host and the second host chose the same ephemeral or random port number.
But the rudder has changed those values to allow it to differentiate between the sessions.
So if traffic comes back to the router going to this destination IP address and port number, the router
knows that it needs to send the traffic to PC one, this PC with this IP address.
But if the traffic comes back from Cisco going to this IP address and port number, so same IP address
but a different port number.
The router knows that it needs to send the traffic to the first PC PC zero.
So that's a nice example of port address translation or Pat creating a unique inside global entries
to allow it to differentiate between different inside local IP addresses.
That is a typical example of what you'll see with a network address translation, but specifically port
address translation where one IP address is being shared between multiple devices on the inside network.
As a last step, I'll save the configuration of the router.
So how did you do?
Were you able to complete the lab?
Did you get it working?
And did you verify that things work properly?
It's important to verify your work.
I want to wish you all the very best.