Networks with redundant paths and devices allow for more network uptime. Redundant topologies eliminate single points of failure. If a path or device fails, the redundant path or device can take over the tasks of the failed path or device.

If Switch A fails, traffic can still flow from Segment 2 to Segment 1 and to the router through Switch B.

If port 1 fails on Switch A then traffic can still flow through port 1 on Switch B.

Switches learn the MAC addresses of devices on their ports so that data can be properly forwarded to the destination. Switches will flood frames for unknown destinations until they learn the MAC addresses of the devices. Broadcasts and multicasts are also flooded.

A redundant switched topology may cause broadcast storms, multiple frame copies, and MAC address table instability problems.

Web Links Understanding Spanning-Tree Protocol – the Fundamental Bridging Algorithm http://www.oreillynet.com/pub/a/ network/2001/03/30/ net_2nd_lang.html