- 18 октомври 2007
Дали ке може да најде нешто (за што служи и слично)за spanning tree protocol.
Превземено од CCNA1:Networking Basics v3.11When multiple switches are arranged in a simple hierarchical tree, switching loops are unlikely to occur. However, switched networks are often designed with redundant paths to provide for reliability and fault tolerance. Redundant paths are desirable but they can have undesirable side effects such as switching loops. Switching loops are one such side effect. Switching loops can occur by design or by accident, and they can lead to broadcast storms that will rapidly overwhelm a network. STP is a standards-based protocol that is used to avoid switching loops. Each switch in a LAN that uses STP sends messages called Bridge Protocol Data Units (BPDUs) out all its ports to let other switches know of its existence. This information is used to elect a root bridge for the network. The switches use the spanning-tree algorithm (STA) to resolve and shut down the redundant paths.
Each port on a switch that uses STP exists in one of the following five states:
A port moves through these five states as follows:
* From initialization to blocking
* From blocking to listening or to disabled
* From listening to learning or to disabled
* From learning to forwarding or to disabled
* From forwarding to disabled
STP is used to create a logical hierarchical tree with no loops. However, the alternate paths are still available if necessary.