Idea of Spanning Tree Protocol..!!!

Dear Valued Reader,

Today we are discuss important protocol of STP. We are think, this protocol is very important our networking sector. So, develop our knowledge……………

Spanning Tree Protocol

Spanning trees accomplish the goal of allowing physical redundancy, but with only one currently active path through a bridged network. Spanning tree uses the following features to accomplish the goal:

A)     All bridge interfaces eventually stabilize at either forwarding or blocking state. The forwarding interfaces are considered a part of the spanning tree.

B)      One of the bridges is elected as root. The election process includes all bridges claiming to be the root, until one bridge is considered best by all. All root bridge interfaces are in forwarding state.

C)      Each bridge receives hello BPDUs from the root, either directly or forwarded by another bridge. Each bridge can receive more than one such message on its interfaces. The port on which the least-cost BPDU is received is called the bridge’s root port. That port is placed in forwarding state.

D)     For each LAN segment, one bridge sends the forwarded BPDU with the lowest cost. That bridge is the designated bridge for that segment. That bridge’s interface on that segment is placed in forwarding state.

E)      All other interfaces are placed in blocking state.

F)      The root sends BPDUs every hellow time seconds. The other bridges expect to receive copies of these BPDUs so that they know that nothing has changed. The hellow time is defined in the BPDU itself, so all bridges use the same value.

G)     If a bridge does not receive a BPDU for Max Age seconds, it begins the process of causing the spanning tree to change. The reaction can vary from topology.(Max Age is defined in the BPDU itself,so all bridges use the same value.)

H)     One or more bridges decide to change interfaces from blocking to forwarding, or vice versa, depending on the change in the network. when moving from blocking to forwarding, the interim listening state is entered first. After the Forward Delay amount of time (another timer defined in the root BPDU), the state is changed to learning. After another Forward Delay amount of time, the interfaces is placed in forwarding state.

I)        When a switch first transitions to a listening state, the switch sends a TCN BPDU over the new path to the root, forcing switches to quickly remove invalid entries from their MAC address tables.

J)       The Spanning Tree Protocol includes these delays to help ensure that no temporary loops occur.