There are three layers, each of which allows you to input certain commands. There's User Mode (also known as User Exec) from where you can only do a number of very limited show commands. Next up is Privileged Mode (Privileged Exec) that takes you into a mode that will allow you to do pretty much any show command you like, although won't allow you to change anything on the device. From this mode you can get to Global Configuration Mode, which does what it says on the tin, as in it allows you to change any configuration on the Switch, affecting it globally. In addition, from this mode you can then move to literally hundreds of other modes, but they are to carry out more specific config.
As well as looking at the command line modes I also spent some time on the boot process of a Switch, their physical indicators and a little initial config, which covered:
- Assigning a Hostname to the Switch;
- Giving the Switch an IP Address & Subnet Mask (Interface vlan 1) that allows connections to the switch remotely through a Telnet session;
- Turning that virtual interface that had just been configured on using the no shutdown command
- Giving the Switch a Default Gateway so if it's destination is not on it's local network, it can get off of that network via it's nearest Router (Default Gateway) to reach it's desired destination;
- Viewing the running config of the Switch to see what changes we had made and then saved them to the Non Volatile Ram of the Switch, so if the device were to reboot or crash the config applied would still be there.
I ended by checking out the Show command Show Version to get info on the hardware, IOS version etc. Let the config continue :)