This is one of multiple videos discussing network address, translation or net.
In a previous video I showed you how to configure static net translations to allow outside hosts or
hosts on the internet access to multiple internal servers running in your local network router to in
this example is netting the three servers on the left to public IP addresses in the 8.8.8 range, making
them available to this PC.
Now the issue here is that you are using an external or public IP address per internal server.
Is it possible to use a single IP address such as an IP address at your home?
To expose multiple servers or devices to the Internet.
So in other words, can you set up servers?
In your home network or small medium business network and allow people to access those servers using
the same IP address.
And the answer is yes.
So at the moment I've got four net commands configured.
What I've done is configure gigabit zero one.
As the outside interface on this router and the other interfaces.
Gigabit zero zero, two and three are configured as inside NAT interfaces.
See my previous video for the configuration of static net using multiple IP addresses once again.
But here what we're going to do is use the command IP nat inside source because we want to net these
servers to an individual IP address.
So I'm going to use the command IP Nat inside source static, the inside local IP address of the server.
In other words, its real IP address is 10.1, 1.1 and we're going to match it to a virtual IP address
of 8.8 to 8.1.
Now, if we did that, we would be using that entire IP address for that individual server.
So what are we going to do here rather is specify TCP IP or UDP.
So TCP IP, and now we're going to specify the inside IP address and the port number on that server
is going to be 23.
And the virtual IP address of the server is going to be this.
And in this example, I'll use Port 23 extendable.
So basically what I'm saying is that when this device sends traffic to Port 23 and destination IP address
8.828.1, the router is going to net it and send the traffic to that server.
So let's test it rather.
Three In this example is acting as our PC, so I'll telnet to 8.8.8.1 and notice I can log in to server
one over there and to prove it we can type show IP interface brief to see the IP address of the server.
Okay.
But now how do you do this?
For the other service.
So in this example, I'm going to use a random port number or a femoral port number of 65,023.
And change that to 10.1, 2.2.
So in other words, when traffic gets sent by this PC to the router with the destination IP address
of 8.8 to 8.1 destination port number of 65,023, the right is going to net it to this internal IP address.
And change the port number to 23.
So on router three.
When we use the Telnet IP address question mark command, we can now specify a port number.
So 65,023.
Connection is opened.
And we are now en route of for.
Show IP interface brief.
We are on router four but.
Using the same.
IP address.
8.8.8.1 but a different port number, which means the traffic goes to a different server.
Let's create another one.
So IP.
Net inside source static TCP IP.
Let's send it to Rada five.
Acting Server three.
But in this case, I'll use a port number of 65,024.
So show run pipe include natch.
Shows us the static net commands.
Let's move that over here I'll exert a lot of for some back end road of three which is acting as our
PC show IP interface brief notice.
This is the IP address of the PC.
It's on the internet.
And what I'll do now is telnet to port.
65,024.
Name one.
Writer five with IP Address 10.1 3.3.
What I'll do now is use the command control shift six X to jump back to router three and go to port
number 65,023.
I'm on rather for control shift six X to jump back show sessions shows me that I've got two sessions
open.
What I'll do now is telnet to port T3.
Now I'm on rather one control shift six x shows that I've got three sessions open.
Show IP Nat en route a two shows me those connections.
So this PC 8.828.4, which is this PC here, has initiated sessions to 828 2 to 8.1 port 23, which
is going to that host.
One of the old TCP sessions is still held in the NAT translation table.
Hence we're seeing two of them.
But we've also got the same PC sending traffic to eight today to date one but port 65,023.
That's going to different host on port 23.
And we've also got this entry.
So that's an example of how to use the same global IP address or Internet IP address for multiple internal
hosts or devices.
So once again, if you were at home and you wanted to make your devices available on the Internet,
but you only had one public IP address, this is how you do it.
The only thing to remember is that you can't use the same port number for multiple internal devices
because otherwise the router can't differentiate between the net translations.
So hence we use different port numbers for the different hosts.
Even though it's the same external IP address.
I hope you've found this useful.
This is out of the scope of a CCNA exam, but hopefully gives you some real world knowledge that you
can apply.
If you enjoyed this video, please like it and I wish you all the very best.