At what level of the Open Systems Interconnection (OSI) do a switch and a bridge operate?
Both operate at layer two. Switches, of course, can segment a network into different parts. Bridges combine different networks together. Routers operate at layer three.
You'll find in-depth information about switches on this SearchNetworking page:
You can also go to this page on SearchSecurity for information on bridges:
For everything you ever wanted to know about OSI, go to SearchNetworking: