STP pvst+

STP (Spanning tree Protocol) Spanning Tree protocol: Changing a ring network structure into a tree structure

1. Logically disconnect the loop to prevent the broadcast storm from producing

2. When the line fails, the blocking interface is activated, resuming communication, and the role of the backup line
3. When there are multiple VLANs in the network, load balancing can be achieved through the application of STP
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Three steps to the algorithm of Spanning Tree protocol:

Select Root Bridge (Root bridge)

Select root port (root Ports)

Select the specified port (Designate Ports)

First understand the cost of the next root path
The root path cost is the sum of the cost of all links on the path to the root bridge of the network Bridge
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The path cost is related to the bandwidth, as shown in the relationship
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The root bridge, the root port, and the specified port are then judged by rules
Experiment
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Experimental steps:
1. Select the root bridge
The root bridge is selected by the bridge ID, which consists of the bridge priority + Bridge's MAC address

The bridge priority is the decimal number used to measure the priority of the bridge in the spanning tree algorithm, the value range is 0~65535, the default is 32768

The bridge MAC address is the MAC address of the switch itself

Select order: The algorithm of the spanning tree is the first priority, the smaller the value is selected as the root bridge, if the priority is the same, then compare the MAC address, the smallest MAC address bridge is the root bridge

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2. Select the root port (select on the switch)
First the root port is present on the non-root bridge, and each non-root bridge will have a root port
Selection Order:

1) lowest root path cost to the root bridge (refers to the port above the switch)
2) Minimum bridge ID for direct connection
3) Minimum port ID (this refers to the port ID value of the peer received)
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3. Select the specified port (select on each line)
First, the port above the root bridge is the specified port, and then each network segment (that is, each line) will have a specified port
Selection Order:
1) low root path cost (refers to the path cost of the switch to the root bridge where the port is located)
2) Small bridge ID value on the switch where the port is located
3) Low Port ID value
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Experimental validation: The Cisco emulator automatically chooses the root bridge, root port, specified port, and blocked port to see if it is the right one, or by commandShowspanning-treeTo view the spanning tree status, respectively, for Switch1, SWITCH2, and Switch3
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Application of STP: pvst+
Pvst+ can realize load balancing of VLAN network
Configuration commands
1) Enable spanning tree
Swtich (config) #Spanning-tree VLANVlan-list
Vlan-list:vlan Serial Number (10 in VLAN 10)
2) There are two ways to specify a root bridge (change the bridge priority and specify a root or Backup bridge)
Ways to change the bridge priority:
Swtich (config) #Spanning-tree VLANVlan-list PriorityBridge-priority
Bridge-priority: Refers to the bridge priority, the default is 32768, the range is 0~65525
Note: If you want to implement VLAN load balancing, the priority configuration of STP must be a multiple of 4096
To specify the root bridge and Backup Bridge method:
Swtich (config) #Spanning-tree VLANVlan-listRoot{Primary | secondary}
{primary | secondary}: Configuration Two Select one, primary for Root bridge, secondary for backup bridge

Common commands in the pvst+ configuration:
modifying port costs
Swtich (config) #Spanning-tree VLANVlan-list CostCost
The second cost is the specific value of the costs such as Swtich (config) #Spanning-tree VLANTen cost19

Modify Port Priority
Swtich (config) #Spanning-tree VLANVlan-listport-priorityPriority
Priority: Refers to the specific value of the precedence such as Swtich (config) #Spanning-tree VLAN10port-priority96

Configure the speed port
Swtich (config-if) #Spanning-tree Portfast

Experiment: Complete the configuration as required
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Experimental steps:
1. Here Switch0 and SWTICH4 do not demonstrate, directly say configuration pvst+ and verify
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2. Close all the ports above the SWITCH1, view the spanning tree above the SWITCH2, and then open the interface above the SWITCH1 to view the spanning tree
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STP pvst+