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This is one of multiple videos discussing net or network address translation.

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In this video we are troubleshooting a net issue we've been told that hosts on the inside network.

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In other words, these hosts which are being represented by right of one, right of four and right of

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five.

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I'm not able to ping 8.8.8.8, which is a Google DNS server.

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And in this example, that's been represented by router three, so we have the inside and the outside

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network router two in this topology is our natural router.

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So let's connect to rather one which is acting as host one and see if it can ping.

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8.8.8.8.

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We're getting an unreachable message in the output here.

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Let's have a look at the routing table.

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This router has a default gateway configured as ten .1.1.254.

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That is rather two in the topology, which is our net router.

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So rather one acting as host, one is able to get to the net Rada.

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But it doesn't look like it's able to get to the Google router.

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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

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get any further.

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Now to speed things up, I'm going to use the no IP domain lookup command.

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And then let's do that trace again so you can see it gets to default Gateway but can't get any further

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than that.

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Let's have a look at the default gateway.

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And see what's happening with the net translations.

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So this is rather to show IP net translations.

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There are no net translations at the moment.

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Show IP net statistics.

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So looking at the statistics, we can see that there have been translations in the past, outside interfaces,

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gigabyte zero one, which is this interface.

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Facing the writer acting as Google inside interfaces.

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Our gigabit to 0002 and zero three.

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In other words, these interfaces over here, a dynamic mapping has been configured for inside source

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address translation.

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We've got a access list pointing to a net pool called Net Pool.

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Can any of the other internal writers ping google?

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So this is root of for.

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Also getting unreachable.

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Let's do a debug ip nat on router two.

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We see a problem here saying that not translation failed.

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Dropping the packet.

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So we're getting a dropped packet from ten.

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One, two, two, which is this router.

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Let's have a look at rather one again so this writer couldn't trace to Google.

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Let's see what happens here.

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We also getting a net translation failure.

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So let's have a look at the configuration.

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Gigabit.

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Zero one is configured with this IP address and it's configured as the outside address show run interface.

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Gigabit zero zero is an example.

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It's configured with this IP address and it's configured as the inside net address.

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Show run pipe include Nat.

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So these are the statements on the interfaces telling us which interfaces are inside and outside.

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If I do a show run pipe, include access.

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Can you see the problem?

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Okay.

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So notice the statement IP Nat inside source list one pull.

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Nat, pull.

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In other words, we saying that any traffic matching access list, one which is permitting anything

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will be netted according to this net pool called net pool.

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But notice here, IP net pool, net pool instead of a net pool is being used.

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So everything else looks good, except we've got a spelling mistake on the net pool name.

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So let's fix that.

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No.

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And I'll remove this command.

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So no IP net pool and then I'll edit that to make it correct.

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So add the extra.

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Oh so show run pipe include net.

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The net pool referenced by the IP statement now exists in the configuration.

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So let's try and do that ping again.

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Ping succeeds.

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And notice we can see that ten 111, which is this rudder.

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Was netted 2828228 ten, which is the first IP address and the net pull for traffic going to 82282828.

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And then when the return traffic came back, this address was netted back to the internal address of

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the writer show IP.

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Net translation shows us that.

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So this inside a local address is being netted to this inside global address.

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The outside address is not being netted.

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So host one can ping google and we see the net translation taking place.

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Host for.

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Can also ping google.com.

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And we've also got another host here.

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Host five, if you like, or.

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Writer five acting as our third host.

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Can it ping Google?

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Yes, it can.

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So that was an example of how to troubleshoot Nat.

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I hope you've enjoyed this video.

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If it's been of benefit to you, please like it and please subscribe to my YouTube channel.

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I wish you all the very best.