The Cisco SG300 switch series can act as a standard layer 2 switch or be enabled for layer 3 functionality. Typically the switch will come in layer 2 mode (also called switch mode in the CLI). There are a couple of ways layer 3 functionality can be enabled and I will demonstrate them both below.
Command Line Configuration
To configure the SG300 to layer 3 or router mode through the command line is very easy. Login through your SSH client of choice and leverage the ‘set system mode’ command. Here you see I have entered part of the command and then hit enter so that it shows the possible options for command completion.
SG300-20#set system mode
router System will run as a IP router
switch System will run as a switch
In our case we want to enable router mode which is of course layer 3 functionality.
SG300-20#set system mode router
Web Console Configuration
Alternatively we can configure the system mode through the web console. Connect to the switch with your browser of choice and navigate to the Administration –> System Settings page.
As you see the system mode is a simple radio button selection. Choose L3 to enable the layer 3 functionality.
Regardless of which method you use to configure the switch a reboot will be necessary so do make sure you have saved your running configuration or you risk losing changes. It is also likely you will be prompted to change the system password when the switch has finished loading.