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The first task in part two is to create a loopback on the router, so on the router interface of loop

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back 0, IP address and I'll create it as follows.

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So show run, shows us the loopback interface and IP address on the router, show start at the moment

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doesn't show us that, we don't have a loopback interface configured, but if I save the configuration

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and type show start again

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notice we can see that the loopback is now part of the start-up configuration.

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We're now told to copy the startup configuration from the server to the start-up configuration of the router.

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So copy TFTP start, 

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before I do that, remember that show start or show startup-config shows us the loopback in the

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configuration, but when I copy the configuration from the TFTP server, will the configuration be overwritten?

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So the source file is R1 start

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config and I'm going to copy it to the startup-config of the router.

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So now when I type show start, notice the loopback has been removed.

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Startup configurations are overwritten, so the running-config currently has

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the loopback configured. If I save the running configuration, in other words, do a copy running-config,

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startup-config, the start-up configuration is overwritten with the running configuration.

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So the start-up config now contains the loopback interface

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but if I copy the configuration from the TFTP server to the startup-config of the router, that original

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config on the TFTP server doesn't contain a loopback.

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So now when I type show startup-config

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the loopback interface has been removed because the configuration on the TFTP server has overwritten

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the startup-config of the router.

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So step five, verify that the startup-config no longer has the loopback interface, 

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we've verified that that is true.

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Startup configurations are overwritten, but what happens was the current configuration.

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So we're told to copy the current config to the TFTP server, so copy running-config TFTP and I'm going

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to call this R1 run V2 config.

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So now on the TFTP server, 

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I have both the original running configuration and the running configuration that I've just copied,

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now we're told to delete the loopback interface on the router at the moment the router has

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a loopback interface configured. So no interface loopback 0

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show IP interface brief, loopback interface has been removed, show run, 

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there's no loopback interface on the router that lets copy the configuration from the TFTP server to the

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running configuration of the router. The file that we're going to copy

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is R1 V2 config, so R1 V2 config,

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copy that to the running configuration that's now being done and notice the loopback interfaces come

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up.

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So show IP interface brief, I'll loopback

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interface has reappeared, 

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show run,

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loopback interface is back.

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Routers do mergers of a running configurations, not overwriting

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and we can prove that by copying the previous running-config from the TFTP server to the router.

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When we originally created this running-config

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there was no loopback interface configured on the router.

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We configured that in task 2, not in task 1, so the router does have a loopback interface at the moment,

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if I say copy TFTP running configuration and copy the original config

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to the running configuration, what you'll notice is the loopback interface still exists.

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This is a merge of configurations.

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The configuration will only be overwritten if there's a conflict

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but the running configuration on the TFTP server didn't have a loopback interface.

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The running configuration on the router did, so it wasn't removed

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but notice the difference

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now, if I change the loopback interface of the router

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to another IP address and now copy the running configuration from the TFTP server

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to the router, but use this version to config where there is a conflict

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and I'll do that again.

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Notice the IP address of the router has been changed.

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So, again, if I change the loopback IP address to this again,

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so that it looks like that and then copy the configuration from the TFTP server to the router

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and do a show IP interface brief, again, this has been overwritten.

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So if there's a conflict, the config that's copied into running-config overrides the conflicting information

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but if there's no conflict, so the router has something that's not on the TFTP server that's not removed.

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So if I created a separate loopback, loopback 2

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this loopback interface will not be removed because that loopback is not in conflict with the configuration

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on the TFTP server.

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In other words, the TFTP server doesn't have loopback 2, so the loopback interface still exists even

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though I've done copy TFTP to running-config, copying to running configuration is a merge, whereas

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copying to startup-config isn't overwriting of the configuration.