Section 4

When you want to connect to a physical router for the first time, it might not have an IP address. To connect to it and configure it we’ll need a console cable and connect it to a computer.

When you start it up for the first time, it’ll ask for a setup dialog. This type of connection is also useful because it allows us to solve problems during boot-up and when the SSH connection is unreliable.

First, we need to enter the privileged exec mode or enabled mode to start using the server. This is done by using the enable command. We can use the ? after a command, it shows all possible keywords for it.

The enabled mode is useful to get information, but to configure a server you use the global mode with the command configure terminal.

You can get to another level for a specific interface (like a ethernet port) by using the interface {type} {name}. To exit this you can use the exit command, which is going to drop us down to the configuration mode.

This can be done from the configuration mode, not in the enabled mode.

It’s normal to make mistakes by executing commands in the wrong command level. When needing to use something from the enable mode, you can prepend a do (like we do with sudo in Linux), to execute the command in the privileged exec mode. This will work on all command levels except the enable level.

• show ip interface brief: it shows all interfaces and their status.
• running-config: show all the current configuration file. It can be more specific by using the run and specify which part of the code we are interested in, or by using a piped command.

• Running configuration: it’s the configuration that’s actually being used.
• Startup configuration: it’s the configuration that’s going to be loaded the next time the router is rebooted.

Normally, changes made are reset on reboot unless it’s specified as a persistent change in the startup config.

Making changes persistent is done by using the command copy run start in the enabled mode. This command can be copied to other places that we can see in the ? command, like the flash memory, scp, etc.

To check contents from a file in the flash memory for example, we can use the more command like this:

more flash:filename