Describe what a layer 3 router is and what are its advantages and drawbacks compared to other network devices.

Did you mean layer 3 switch? Because a router always operates at layer 3

Explanation:

If the answer is yes, then a layer 3 is a switch that combines the functions of a switch and a router. So it is capable of operate layer 2 and layer 3. Some of its benefits are: Support routing between VLAN, decrease network latency because the packets don't have to make extra hops to go through a router and reduce security management. But they are really expensive and lack of WAN functionality so they are used mostly for large intranet environments.