7.2 Spanning-Tree Protocol  
  7.2.3 Spanning-tree operation  
When the network has stabilized, it has converged and there is one spanning tree per network.

As a result, for every switched network the following elements exist:

  • One root bridge per network
  • One root port per non root bridge
  • One designated port per segment
  • Unused, non-designated ports

Root ports and designated ports are used for forwarding (F) data traffic.

Non-designated ports discard data traffic. These ports are called blocking (B) or discarding ports.

 

Web Links

Understanding Spanning-Tree Protocol

http://www.cisco.com/univercd/cc/
td/doc/product/rtrmgmt/sw_ntman/
cwsimain/cwsi2/cwsiug2/vlan2/stpapp.htm