Console

In first time, we connect to router or switch with console cable. We have to secure this connection.

When you entered router, you are in user exec mode, like:

Router>
Switch>

You need to jump into privileged exec mode:

enable

It look like this:

Router#
Switch#

Go to global configuration mode with:

configure terminal

After that command, you see like this:

Router(config)#
Switch(config)#

Select console line with:

line console 0

It gives:

Router(config-line)#
Switch(config-line)#

Now we cat put password on that line:

password 123
login

It's done, you can exit with exit command

You can encrypt that password in global configuration mode with:

service password-encryption