As switches established themselves in networks, vendors added increasing
functionality. Modern switches can perform forwarding decisions based on
Layer 3 routing, as well as on Layer 4 and above. Even though switches can
perform the functions of other higher-layer devices such as routers and content
switches, you still must separate these functionalities to avoid single points of
failure. Switches are the workhorse of networks, providing functionality across
almost all layers of the OSI model reliably and quickly. Switches can also provide
power to devices such as IP-based phones using the same Ethernet connection.
Again, this applies to very large switches serving corporate networks
rather than the switches in a small office or home.