This is one of multiple videos discussing network address translation or not in a previous video I showed
you how to configure static Nat translations to allow outside hosts hosts on the Internet access to
multiple internal servers running in your local network router to in this example is nothing the three
servers on the left to public IP addresses in the 8 8 8 range making them available to the 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 0 1 as the
outside interface on this router and the other interfaces gigabit 00 two and three are configured as
inside Nat interfaces.
See my previous video for the configuration of static not using multiple IP addresses once again.
But here what we're going to do is use the command IP not inside source because we want to Nat these
servers to an individual IP address.
So when we use the common IP Nat inside source static The inside a local IP address of the server.
In other words it's real IP addresses tend wondered wondered one.
And we get to a virtual IP address of 8 8 8 8 to 1.
If we did that we would be using that entire IP address for that individual server.
So what we're going to do here rather is specify TCAP or UDP.
So TZP And now we are 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 8 8 8 1 the router is going to Nottage and send the traffic to that server.
So let's test at rather three in this example is acting as our PC.
So all telnet to 8 8 8 to 1.
Notice I can log in to server 1 over there and to prove it we can type show IP interface brief to see
the IP address of the server
OK but now how do you do this for the other service.
So in this example I'm going to use a random port number that we femoral port number of 65000 23 and
change that to tendered one to two to two.
So in other words when traffic gets sent by the PC to the router with the destination IP address of
8 8 8 8 or 1 destination port number of 65000 and 23 the road is going to not get to us internal IP
address.
And change the port number to 23 so on Rodda 3 when we use the telnet IP address question mark C'mon
we can now specify a port number.
So sixty five thousand twenty three connection is opened and we are now on route a full
show IP interface brief.
We are on route a full but using the same IP address 8 8 8 or 1 but a different port in them which means
the traffic goes to a different server.
Let's create another one.
So IP not inside source.
Static TZP
Let's send it to route of five acting service free.
But in this case I'll use a port number of 65000 and 24 hour show run pipe include Nat shows us the
static Nat commands that over here in Colorado for some back on Route 3 which is acting as our PC show
at the 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 sixty Falzon and 24
now I'm on route 5 with IP address 10 at one of 3.3.
What I'll do now is use the command control shift 6 x to jump back to Route 3 and go to port number
65000 23 on write a full control shift 6 x to jump back shows sessions.
Shows me that I've got two sessions open what I'll do now is telnet to port 23.
Now I'm on route 1 controllers shift 6 x shows that I've got three sessions open show IP not on router
2 shows me those connections.
So this PC 8 8 today or four which is this PC here has initiated sessions 2 8 8 8 8 1 pt. 23 which is
going to that host one of the old TZP sessions is still held in the NAT translation table.
Hence we are seeing two of them but we've also got the same PC sending traffic to eight today today
day one but Port sixty five thousand twenty three that's going to a 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're 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 that translations.
So hence we use different port numbers for the different hosts.
Even though it's the same external IP address I hope you found this useful.
This is out of the scope of a CCMA exam but hopefully give you some real world knowledge that you can
apply.
If you enjoyed this video please like it.
I wish you all the very best.