When is a Router on a Stick Most Appropriate?

A

A router on a stick is a networking configuration where a single physical interface on a router is divided into multiple logical interfaces (sub-interfaces), each with its own VLAN ID. The router then uses a trunking protocol such as IEEE 802.1Q to carry traffic between the sub-interfaces and the corresponding VLANs on the network.

The most appropriate circumstance for using a router on a stick is when a router has multiple subnets on a single physical link. This scenario is typically found in situations where a switch is connected to a router, and the switch has multiple VLANs configured on it.

By configuring the router with sub-interfaces, each associated with a different VLAN ID, the router can communicate with devices on each of the VLANs, without the need for multiple physical interfaces. This setup is known as a "router on a stick" because a single physical interface on the router is used to carry traffic to and from multiple subnets, just like a stick with multiple branches.

Option A is the correct answer because it accurately describes the scenario where a router on a stick is most appropriate. Option B, when a router has a single subnet on multiple physical links, would not require a router on a stick as the router would have separate physical interfaces for each link. Option C, when a router has multiple interfaces on a single physical link, would not require a router on a stick because the router already has multiple physical interfaces. Option D, when a router has a single interface on multiple physical links, is not a scenario where a router on a stick would be appropriate as the router does not have multiple subnets to communicate with.