Performance penalty or cons to enabling Layer 3 mode?

[Bob Smith]

I recently purchased an SG300 switch and was not aware that Layer 3 was disabled by default. To enable it, I'd have to reset my whole config and start over again.

Is there any performance penalty to enabling Layer 3 mode on the switch? If not, then why would it be disabled by default? What am I missing here?

[devils_advocate]

Hey Bob

The Small Business switches are Layer 2 by default with the ability to have basic Layer 3 features if needed. When buying one, it comes Layer 2 out of the box so you can literally plug in hosts and you have an unmanaged switch.

Obviously even in L2 mode, its technically a managed switch as you can create Vlans but its not much use doing that unless you have a Layer 3 device somewhere on your network. 

As far as I am aware there is no performance hit, the SG series are not the best performing switch in the Cisco range anyway so even if there were, you are likely not going to notice any performance hit. If you wanted performance, you wouldn't have bought a small business switch right ? :)

It is frustrating that you have to wipe the config to go Layer 3 but unless you NEED the L3 features then just leave it as Layer 2.

I can't answer the question of why the come Layer 2 by default, my assumption is that because they are entry level switches designed for small business, having them Layer 2 means they will work right out of the box as a basic unmanaged switch.

Thanks