The first task in part two is to create a loopback on the router, so on the router interface of loop
back 0, IP address and I'll create it as follows.
So show run, shows us the loopback interface and IP address on the router, show start at the moment
doesn't show us that, we don't have a loopback interface configured, but if I save the configuration
and type show start again
notice we can see that the loopback is now part of the start-up configuration.
We're now told to copy the startup configuration from the server to the start-up configuration of the router.
So copy TFTP start,
before I do that, remember that show start or show startup-config shows us the loopback in the
configuration, but when I copy the configuration from the TFTP server, will the configuration be overwritten?
So the source file is R1 start
config and I'm going to copy it to the startup-config of the router.
So now when I type show start, notice the loopback has been removed.
Startup configurations are overwritten, so the running-config currently has
the loopback configured. If I save the running configuration, in other words, do a copy running-config,
startup-config, the start-up configuration is overwritten with the running configuration.
So the start-up config now contains the loopback interface
but if I copy the configuration from the TFTP server to the startup-config of the router, that original
config on the TFTP server doesn't contain a loopback.
So now when I type show startup-config
the loopback interface has been removed because the configuration on the TFTP server has overwritten
the startup-config of the router.
So step five, verify that the startup-config no longer has the loopback interface,
we've verified that that is true.
Startup configurations are overwritten, but what happens was the current configuration.
So we're told to copy the current config to the TFTP server, so copy running-config TFTP and I'm going
to call this R1 run V2 config.
So now on the TFTP server,
I have both the original running configuration and the running configuration that I've just copied,
now we're told to delete the loopback interface on the router at the moment the router has
a loopback interface configured. So no interface loopback 0
show IP interface brief, loopback interface has been removed, show run,
there's no loopback interface on the router that lets copy the configuration from the TFTP server to the
running configuration of the router. The file that we're going to copy
is R1 V2 config, so R1 V2 config,
copy that to the running configuration that's now being done and notice the loopback interfaces come
up.
So show IP interface brief, I'll loopback
interface has reappeared,
show run,
loopback interface is back.
Routers do mergers of a running configurations, not overwriting
and we can prove that by copying the previous running-config from the TFTP server to the router.
When we originally created this running-config
there was no loopback interface configured on the router.
We configured that in task 2, not in task 1, so the router does have a loopback interface at the moment,
if I say copy TFTP running configuration and copy the original config
to the running configuration, what you'll notice is the loopback interface still exists.
This is a merge of configurations.
The configuration will only be overwritten if there's a conflict
but the running configuration on the TFTP server didn't have a loopback interface.
The running configuration on the router did, so it wasn't removed
but notice the difference
now, if I change the loopback interface of the router
to another IP address and now copy the running configuration from the TFTP server
to the router, but use this version to config where there is a conflict
and I'll do that again.
Notice the IP address of the router has been changed.
So, again, if I change the loopback IP address to this again,
so that it looks like that and then copy the configuration from the TFTP server to the router
and do a show IP interface brief, again, this has been overwritten.
So if there's a conflict, the config that's copied into running-config overrides the conflicting information
but if there's no conflict, so the router has something that's not on the TFTP server that's not removed.
So if I created a separate loopback, loopback 2
this loopback interface will not be removed because that loopback is not in conflict with the configuration
on the TFTP server.
In other words, the TFTP server doesn't have loopback 2, so the loopback interface still exists even
though I've done copy TFTP to running-config, copying to running configuration is a merge, whereas
copying to startup-config isn't overwriting of the configuration.