This is one of multiple videos discussing net or network address translation.
In this video we are troubleshooting a net issue we've been told that hosts on the inside network.
In other words, these hosts which are being represented by right of one, right of four and right of
five.
I'm not able to ping 8.8.8.8, which is a Google DNS server.
And in this example, that's been represented by router three, so we have the inside and the outside
network router two in this topology is our natural router.
So let's connect to rather one which is acting as host one and see if it can ping.
8.8.8.8.
We're getting an unreachable message in the output here.
Let's have a look at the routing table.
This router has a default gateway configured as ten .1.1.254.
That is rather two in the topology, which is our net router.
So rather one acting as host, one is able to get to the net Rada.
But it doesn't look like it's able to get to the Google router.
So you can see in the output here, it's reached ten .1.1 or 2.54, but it doesn't look like it can
get any further.
Now to speed things up, I'm going to use the no IP domain lookup command.
And then let's do that trace again so you can see it gets to default Gateway but can't get any further
than that.
Let's have a look at the default gateway.
And see what's happening with the net translations.
So this is rather to show IP net translations.
There are no net translations at the moment.
Show IP net statistics.
So looking at the statistics, we can see that there have been translations in the past, outside interfaces,
gigabyte zero one, which is this interface.
Facing the writer acting as Google inside interfaces.
Our gigabit to 0002 and zero three.
In other words, these interfaces over here, a dynamic mapping has been configured for inside source
address translation.
We've got a access list pointing to a net pool called Net Pool.
Can any of the other internal writers ping google?
So this is root of for.
Also getting unreachable.
Let's do a debug ip nat on router two.
We see a problem here saying that not translation failed.
Dropping the packet.
So we're getting a dropped packet from ten.
One, two, two, which is this router.
Let's have a look at rather one again so this writer couldn't trace to Google.
Let's see what happens here.
We also getting a net translation failure.
So let's have a look at the configuration.
Gigabit.
Zero one is configured with this IP address and it's configured as the outside address show run interface.
Gigabit zero zero is an example.
It's configured with this IP address and it's configured as the inside net address.
Show run pipe include Nat.
So these are the statements on the interfaces telling us which interfaces are inside and outside.
If I do a show run pipe, include access.
Can you see the problem?
Okay.
So notice the statement IP Nat inside source list one pull.
Nat, pull.
In other words, we saying that any traffic matching access list, one which is permitting anything
will be netted according to this net pool called net pool.
But notice here, IP net pool, net pool instead of a net pool is being used.
So everything else looks good, except we've got a spelling mistake on the net pool name.
So let's fix that.
No.
And I'll remove this command.
So no IP net pool and then I'll edit that to make it correct.
So add the extra.
Oh so show run pipe include net.
The net pool referenced by the IP statement now exists in the configuration.
So let's try and do that ping again.
Ping succeeds.
And notice we can see that ten 111, which is this rudder.
Was netted 2828228 ten, which is the first IP address and the net pull for traffic going to 82282828.
And then when the return traffic came back, this address was netted back to the internal address of
the writer show IP.
Net translation shows us that.
So this inside a local address is being netted to this inside global address.
The outside address is not being netted.
So host one can ping google and we see the net translation taking place.
Host for.
Can also ping google.com.
And we've also got another host here.
Host five, if you like, or.
Writer five acting as our third host.
Can it ping Google?
Yes, it can.
So that was an example of how to troubleshoot Nat.
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