STP algorithm and pvst+ for load balancing

Experimental project:
1> Understanding how spanning Tree Protocol [STP] works
2> configuration pvst+ for load balancing.
The experiment passed:
One: Principle: 1. In the actual network environment, the physical loop can improve the reliability of the network. But in a switched network, when the switch receives a data frame from an unknown destination, it broadcasts the data. In this case, in a switched network where there is a physical loop, a two-way broadcast ring is generated, and the broadcast storm causes the switch to crash, so it generates STP.
The 2.STP protocol is a logical disconnection of the network loop to prevent broadcast storms, and if the line that is being used fails, then logically disconnected lines will be connected and continue to transmit data.
The 3.STP protocol is a network of physically existing loops that, through an algorithm, logically blocks some ports to generate a logical tree structure.

   二:  STP算法：它的算法分为三个步骤分别是   1》选择根网桥----它的依据就是网桥ID。网桥ID的结构是网桥优先级和往前的MAC地址。优先级小的被选为根

Network Bridge. If the priority is the same, select a small MAC address as the root bridge

2 Select the root port----root port exists on a non-root bridge, you need to select a root port on each non-root bridge. Select root port required by: to the Root bridge
Lowest root path cost, minimum direct-link bridge ID, minimum port ID

3 Select a specified port---it also requires 3 steps to complete. The root path cost is lower, where the switch bridge ID is small and the port ID value is small. Here you need
Note that the ports on the root bridge are the specified ports because the port root path cost on the root bridge is 0

      四：  BPDU [桥协议数据单元] ：交换机之间是通过BPDU来交换网桥ID，根路径成本等信息。            BPDU [桥协议数据单元]：两种类型         1》配置BPDU------用于生成树计算                                                      2》拓扑变更通告------用于通告网络拓扑的变化      五：  在STP计算过程中，交换机的每一个端口都必须依次经历五种状态：1.转发  2.学习  3.侦听  4.阻塞   5.禁用  

The pvst+ is developed by Cisco and facilitates interoperability with other vendors ' implementations that run spanning trees on VLANs. Pvst+ generates a spanning tree instance for each VLAN, each of which consumes the CPU and memory of the switch. The multiple spanning tree defined by Ieee802.1s is used to resolve excessive spanning tree problems. There are two meanings of configuring pvst+: 1. Using pvst+ to achieve Network Load Balancing 2. Configure the speed port "Enable speed port will save 30S of forwarding time delay"

1. Let's do an experiment to verify. First of all, we still build the topology diagram in the virtual machine GNS3, and mark all the parameters that are needed. Such as:

2. Although this topology is simple, let's analyze it first, and we need to do those configurations. First, each port needs to be made into a trunk port, followed by the addition of two VLANs, and finally we will do pvst+. Let's start with the configuration on the SW1. Such as:

3. The other two configurations as in the previous step, do not repeat here. Let's configure pvst+. Such as:

4. What needs to be said here is that when SW2 becomes Vlan20 's Root bridge, the Vlan20 data will go SW2. When there is a problem with the link between SW1 and SW2, the Vlan20 will go on the other side, thus achieving load balancing. SW3 is also the same configuration, the SW3 into a VLAN root bridge. Such as:

5. Let's now look at the port that it's blocking. Such as:

6. You can also check the other VLAN to see which is the blocking port.
Summary: 1 The steps to know the spanning tree algorithm: First select the root bridge, then select the root port, and finally select the specified port.
2 "switch is to exchange Network Bridge ID, root path cost and other information through BPDUs
3 "Spanning tree port has five states: Disable, block, listen, learn, forward.
4 "Familiar with pvst+ for load balancing

STP algorithm and pvst+ for load balancing