This is one of multiple network address translation or NAT troubleshooting videos.
In this topology, we've been told that hosts on the inside network rather one acting as host one we're
out of four acting as host two and wrote a five acting as host three are not able to ping router three
acting as google rather tune.
This topology is configured as the nat rudder.
So let's do some verification on rather one each rather one able to ping the Google server 8.8.8 to
date.
And at the moment it's not.
Let's do a debug on router two acting as our natural rudder.
So debug pipe net.
Do the ping again.
We are not getting any output on the console and we are monitoring bugs on the console at the moment.
So let's verify that traffic is getting to the default gateway.
In this example, the router has a default gateway of ten .1. 1 to 2.4, so paying 10.1 to 1 to five
for traffic gets to the default gateway.
Let's trace to google.com.
Traffic gets to the default gateway.
Which is rather too in this example.
It gets no further.
So the trace is timing out.
So let's determine if the problem is on the net rudder.
So show IP net statistics shows us statistics of the net configuration.
Here's the command.
We don't have any active translations.
The outside interface is gigabit zero one, which is correct per a diagram inside interfaces or gigabit
0002 and zero three, which is correct per our diagram.
We have a dynamic translation configured for inside source addresses.
We're using access list one and a Nat pool called the Nat Pool, which has this subject mask and this
range of addresses.
So let's do some more investigation show run pipe include net.
These are the commands on the various interfaces we were able to see which interfaces had NAT configured
through this output here.
So we know that some interfaces are configured as inside and one is configured as outside.
And that's what this config is showing.
You could, if you wanted to make sure use commands such as show run interface and a individual interface
such as gigabit zero one to confirm that the NAT has been configured correctly on the interface.
But these statistics command has shown us that output already it's a show run pipe include Nat we can
see here that a net command has been configured netting inside source addresses using access list one
and a nat pool called Nat Pool, which is configured here.
And we can see a range of addresses in the pool and a subnet mask.
Show access lists.
We've got access list one configured and that's what's been referenced in the net statement and we have
some matches in the access list.
Show IP interface brief.
Can you see the problem?
Let's have a look at rather for show IP interface brief.
Can you see.
The problem here.
Let me give you another hint.
Show interface gigabit.
Zero zero.
Show Run.
Interface Gigabit.
200.
And on router four.
Show Run.
Interface gigabit.
Zero zero.
Can you see the problem?
Here's another hint show run pipe.
Include access.
Look at how this access list is configured.
Compare that to the IP addresses of the host devices.
Okay.
So notice this host is in subnet ten 120.
This host is in subnet ten 110 slash 24 mask.
Here.
However, the access list is matching ten zero 110 zero two and ten zero three host five acting as our
third internal PC.
Has an IP address ten 133 slash 24.
The success list is incorrect.
So no access list, one access list one permit ten 110 slash 24.
Ten 120 2410 130 slash 24.
So show access list.
This access list looks better.
Let's confirm that networks are paying.
8.8.8.8.
Ping succeeds.
We see the net translations on router two for that host.
Pink.
8.828.8.
Pings succeed and we see the net translations.
And en route of five of third internal host ping succeed and we see the net translations.
So be careful with your access lists.
Your access lists have to match your net statements and be correct for the hosts in the topology.
This net statement is matching access list one access list one is now correctly configured.
So we see matches on the access list.
That was an example of troubleshooting network address translation.
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