- [Instructor] So since we have a fundamental
understanding of PAT now NAT overload,
let's go out and have some fun, configure NAT overload.
Now this is something that you're going to do
on a corp at your home or work,
something real a lot of fun.
The first thing we want to do,
there's just a couple of different ways to do this.
Of course we can create a pool.
That's an easy way to do it but the best way
to do it and for the objectives is to create
an even easier way where I'm going to use
my interface, alright so check this out,
so you want to say ip nat, inside source
can use list 1 which I haven't created yet
and use my interface, s0/0/1, that's my outside interface
that has a global IP address, I could press enter here.
But wait, I want to overload it.
Now I probably should create the list too
so access list, two more cans, access list 1
permit 10.1.1.0.0.0.0.255 and then just one more line
and I'm done and I can have over 60,000 users
get out with one IP address.
And I want to make sure that my interfaces are marked
so I'm going to s0/0/1 is my ip nat outside,
interface s/0/1/1 ip nat inside,
this is all I need to do.
I don't need a bunch of commands, I don't need a pool.
I can come out here and overload by using
my outside interface on my router going
to the internet as my inside global.
Let's go out to the PC and first thing
we're going to do is ping 209.165.201.1,
and then telnet to the internet
and see that we can get out to the internet.
And we'll be able to see the translation,
I'll just back out a little bit,
show ip net, translations and statistics,
and so I'll do translations and notice
I just have one connection in here that my
inside local and my inside global right,
this inside global is really my outside local
or the router interface, 209.165.201.1.
Now this port number 55891 which was used
to telnet out to the internet is how it's going
to remember me, so my outside local
is my destination obviously but let me see
if I can ping again so this isn't going
to stay in very long.
See if I can capture it.
So it obviously worked it crated in there
but it comes in and out really quick.
There are a couple other commands that we want
to take a look at, okay show ip nat statistics.
Okay that's where I was, so and then I did a show
access list, okay and then show run.
Let's run out and just verify our interfaces,
the show run command, go all the way down
to our serial interfaces here.
Serial0/0/1 and serial1/0/1/1 and we can
see our ip nat inside and outside.
So if I did a show ip nat translations
I don't see anything in there anymore.
But if I did because it did come out,
so I'm going to type internet again
and we're going to go in there, I'm in corp.
Okay so we'll see that that's in there.
So let's come out to corp show ip nat translations,
and then we'll see it in there.
Let's say that I want to clear this out,
it was stuck, I want you to be careful
with what I'm about to show you.
It could cause some problems in production.
First off you can do debug ip nat.
You should only use this command if you're having a problem
because it's going to give you a lot of traffic.
So if I went back out here again
and to the router and exit and then internet
and then went back in, looking at the output
of this command we can see a few things.
First off, nat asterisk means it was fast switched
to the x interface which is a package switching technology,
and then we can see the source 10.1.1.2,
that's my inside local.
And my inside global is 209.165.201.1.
Right that is my inside global which is
the same thing as my outside local,
right so we're using the x interface
or the outside interface of my router
and then we have our outside global which is
the destination, and then we can see it come back.
Alright so we can see that it's going to clear it out,
that it's expiring, but one of the things I can do
is if you're having problems what they call
thrashing of the nat table people are coming
in and out because it's just so busy,
clear ip nat and I want you to be careful with this one
and I can do asterisk.
This will clear my whole table,
now I can do it by hand but I can clear my whole table,
core ip nat translations.
Remember this will bring everyone down on reset,
every session you have in your corporate network.
So I can use command to be to bug ip nat,
clear ip nat translations asterisk,
use them carefully in production but when you're
studying for your exam objectives
you do want to use them and know them
when you're doing your lab, but again just
be careful in production.
So that's going to conclude our nat labs,
our static dynamic in nat overload
as well as an easy way to configure them,
and I also showed you a great way to verify them.