Building Redundancy Switched Topologies Flashcards
Without some loop-avoidance process, each switch floods broadcast, multicast, and unknown unicast frames endlessly. Switches flood broadcast frames to all ports except the port on which the frame was received. The frames then duplicate and travel endlessly around the loop in all directions. The result of continuous broadcast frame duplication is called a broadcast storm.
Continuous frame duplication
Multiple copies of unicast frames may be delivered to destination stations. Many protocols expect to receive only a single copy of each transmission. Multiple copies of the same frame can cause unrecoverable errors.
Multiple frame transmission
Instability in the content of the MAC address table results from the fact that different ports of the switch receive copies of the same frame. Data forwarding can be impaired when the switch consumes the resources that are coping with instability in the MAC address table.
Media Access Control (MAC) database instability
This port exists on non-root bridges. It is the switch port with the best path to the root bridge. Root ports forward traffic toward the root bridge and populate the MAC address table for network segments attached to that port. Only one root port is allowed per switch or per VLAN in Cisco PVST+.
Root port
This port exists on root and non-root bridges. For root bridges, all switch ports are designated ports. For non-root bridges, a designated port is the switch port that will receive and forward frames toward the root bridge as needed. Only one designated port is allowed per segment.
Designated port
The nondesignated port is a switch port that it is blocking data frames and is not populating the MAC address table with the source addresses of frames that are seen on that segment.
Nondesignated port
The disabled port is a switch port that is shut down.
Disabled port
