Which statement is correct about implementing ROAS?

A. Each IP address is configured on the subinterface as the gateway for the VLAN.
B. The main interface must be configured with the summary IP address for all VLANs.
C. You must configure at least one native VLAN.
D. All of the above

A. Each IP address on a subinterface is the routed gateway for the VLAN on that subinterface. The main interface should be configured with the no ip address command when ROAS is configured. The default native VLAN of 1 is configured on the switch side only unless you explicitly configure a native VLAN on the router.

Router-on-a-stick (ROAS) is a technique to connect a router with a single physical link to a switch and perform IP routing between VLANs. From the switch's perspective, this physical link is configured as a trunk port allowing all VLANs that are going to be routed.