This is one of multiple network address translation or NAT videos.
This is a troubleshooting video.
In this scenario, you've been told that some hosts in the internal network are not able to connect
to the Internet.
In this Janus three topology.
I've got four routers, router two and router three are acting as PCs.
They have IP routing disabled, they have their default gateways configured as router one.
Rather, one is going to act as our network address.
Translation router and router four is going to act as Google.
So let's test the network can write a one ping the DNS server.
So router four pretending to be the Google DNS server.
Yes, it can.
What about rather three?
Doesn't look like it's able to ping.
Let's investigate.
So show IP rot.
We can see that IP routing is disabled on this router, but it's default gateways configured as ten
111.
What about on rather to rather to has the same configuration.
Wrote to campaign ten 111 and can ping google router three can ping ten 111.
We could trace to google.
It gets to its default gateway ten 111.
But then nothing happens.
So we have a timeout on rudder one.
So on router one, let's confirm the IP address in firstly.
If zero one has an IP address of ten 111.
That's the inside of the network.
If zero zero has an IP address of 8228228244.
So let's do a debug on the strata.
Debug I peanut.
Wrote it too.
Was able to ping Google before and still can and we can see the natural translation taking place.
When rudder three pings google.com.
We don't see any net translations.
Show IP.
Net translations.
So we see a net translation for.
REPORTER two That's the IP address of WRITER two So show IP Interface Brief will show us that.
So we can see the net translation four out of two.
But we don't see a net translation.
Four out of three.
What happens if we clear the net translations?
So there are no natural translations at the moment.
When I ping from router three to Google we suddenly see translations.
And the pings start succeeding.
So Ken rather to paying google.com.
Notice four out of two now no longer paying google.com.
Let's clear the net translations again.
Rather two is now able to paint google.com.
But rather three is not.
So it looks like when we clear the net translations, one device is able to connect to Google should
run.
If zero zero is correctly configured with an IP address and is configured as the outside NAT interface.
If 0/1 has the correct insight IP address and is configured as the inside NAT interface.
Okay.
Can you see the problem?
What's going on here?
Notice we're not clear the net translation again.
And then ping from Writer three, which wasn't able to ping previously.
The pings now succeed show IP net translation we now see a net translation four out of three.
So going back through the configuration and I'll scroll down to the net config.
Can you see the problem?
Okay.
Have a look at this IP Nat inside source list one which is pointing to access list one that means that
any IP address will be netted, but it's pointing to a pool called my pool.
The net pool is configured with a starting IP address of 82828 8 to 2 and an ending IP address of 8.8.
8 to 2.
That means we've only put one IP address in the pool.
Hence only one internal host can be netted at any given time.
So let's remove this.
We told her we can't remove it.
So let's clear the IP net translations.
Translation star.
And try and remove it again.
So it's removed now.
What we should do is add additional IP addresses to the pool, so I'll add from 2 to 20.
Previously it was from 8 to 8 two 8 to 2 to 8282822.
But now it's going from 2 to 20.
So show run pipe include.
Net will show us that configuration.
So Ken wrote a three ping.
Google.
Yes, it can can run a two ping Google.
Yes, it can.
It took it a while, but rather to campaign Google, write a three campaign Google and we see the net
translations for both of them.
Notice please, that the one device is netted.
28282823 and the other one is netted 282882 data to the show IP net translation shows us that two addresses
in the pool have been used.
Show IP net statistics.
At the moment we have six dynamic translations.
Notice our poll shows us the list of IP addresses.
So we have a starting address of 8.82822 and ending of 82822 820.
There are 19 addresses in the pool and two have been allocated, so this would be another good command
to use.
Let's clear the net.
Translation and remove the command.
And I'll edit back.
With only a single IP address in the pool.
To show IP net translations.
No translations at the moment.
Show IP net statistics.
Notice we only have one IP address in the pool.
So when router three pings.
And we look at the statistics again.
Notice 100% of the pool is allocated.
So that's why Writer two is not able to ping because the, because the pool consists of a single IP
address and it's already been allocated.
So again, be careful with your pools.
You need to allocate enough addresses to the pool.
So clear the net translations again.
Well, remove.
That pool.
Configure it again with.
Let's say, from 2 to 25 to show IP net statistics.
We have 24 dresses in the pool in this range.
None have been allocated.
I'll send some traffic from both writer to and writer three.
So we can see that rather too is being netted and so is rather three.
And now when we look at the statistics.
Notice 24 addresses are available to have been allocated.
So that was an example of how to troubleshoot, network address translation or NAT.
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