<P> While switches may learn about topologies at many layers, and forward at one or more layers, they do tend to have common features . Other than for high - performance applications, modern commercial switches use primarily Ethernet interfaces . </P> <P> At any layer, a modern switch may implement power over Ethernet (PoE), which avoids the need for attached devices, such as a VoIP phone or wireless access point, to have a separate power supply . Since switches can have redundant power circuits connected to uninterruptible power supplies, the connected device can continue operating even when regular office power fails . </P> <P> A network hub, or a repeater, is a simple network device that does not manage any of the traffic coming through it . Any packet entering a port is flooded out or "repeated" on every other port, except for the port of entry . Specifically, each bit or symbol is repeated as it flows in (with a minimum delay for the line interface). Due to this, a repeater hub can only receive and forward at a single speed . Since every packet is repeated on every other port, packet collisions affect the entire network, limiting its overall capacity . </P> <P> There are specialized applications in which a network hub can be useful, such as copying traffic to multiple network sensors . High - end network switches usually have a feature called port mirroring that provides the same functionality . </P>

Where does switch belong to in osi layer