Example for Configuring RSTP

Networking Requirements

On a complex network, multiple physical links are often deployed between two devices for link redundancy (one as the active link and the others as standby links). However, redundant links may cause loops on the network, which result in broadcast storms and unstable MAC address entries.

RSTP can be deployed on a network to eliminate loops by blocking ports. In Figure 1, a loop exists on the network, and SwitchA, SwitchB, SwitchC, and SwitchD are all running RSTP. These devices exchange BPDUs to discover the loops and block the appropriate ports in order to trim the ring topology into a loop-free tree topology, improving packet processing performance.

Figure 1 Networking diagram of basic RSTP configurations

Configuration Roadmap

The configuration roadmap is as follows:

Configure basic RSTP functions.
1. Configure the RSTP mode for the switches on the ring network.
2. Configure the root bridge and secondary root bridge.
3. Set a path cost for the ports to be blocked.
4. Enable RSTP to eliminate loops. Because ports connected to the PCs do not participate in RSTP calculation, configure both of these ports as edge ports.
Configure RSTP protection functions. For example, configure root protection on designated ports of the root bridge.

Procedure

Configure basic RSTP functions.
1. Configure the RSTP mode for the switches on the ring network.
  
  # Configure the RSTP mode on SwitchA.
```
<HUAWEI> system-view
[HUAWEI] sysname SwitchA
[SwitchA] stp mode rstp
```
  # Configure the RSTP mode on SwitchB.
```
<HUAWEI> system-view
[HUAWEI] sysname SwitchB
[SwitchB] stp mode rstp
```
  # Configure the RSTP mode on SwitchC.
```
<HUAWEI> system-view
[HUAWEI] sysname SwitchC
[SwitchC] stp mode rstp
```
  # Configure the RSTP mode on SwitchD.
```
<HUAWEI> system-view
[HUAWEI] sysname SwitchD
[SwitchD] stp mode rstp
```
2. Configure the root bridge and secondary root bridge.
  
  # Configure SwitchA as the root bridge.
```
[SwitchA] stp root primary
```
  # Configure SwitchD as the secondary root bridge.
```
[SwitchD] stp root secondary
```
3. Set a path cost for the ports to be blocked.
  
  The path cost value range depends on path cost calculation methods, which must be the same on all switches. This example uses the Huawei proprietary calculation method.
  
  # On SwitchA, set the path cost calculation method to the Huawei proprietary method.
```
[SwitchA] stp pathcost-standard legacy
```
  # On SwitchB, set the path cost calculation method to the Huawei proprietary method.
```
[SwitchB] stp pathcost-standard legacy
```
  # On SwitchC, set the path cost of GigabitEthernet0/0/1 to 20000.
```
[SwitchC] stp pathcost-standard legacy
[SwitchC] interface gigabitethernet 0/0/1
[SwitchC-GigabitEthernet0/0/1] stp cost 20000
[SwitchC-GigabitEthernet0/0/1] quit
```
  # On SwitchD, set the path cost calculation method to the Huawei proprietary method.
```
[SwitchD] stp pathcost-standard legacy
```
4. Enable RSTP to eliminate loops.
  - Configure the ports connected to PCs both as edge ports.
    
    # Configure GigabitEthernet0/0/2 on SwitchB as an edge port.
```
[SwitchB] interface gigabitethernet 0/0/2
[SwitchB-GigabitEthernet0/0/2] stp edged-port enable
[SwitchB-GigabitEthernet0/0/2] quit
```
    (Optional) Configure BPDU protection on SwitchB.
```
[SwitchB] stp bpdu-protection
```
    # Configure GigabitEthernet0/0/2 on SwitchC as an edge port.
```
[SwitchC] interface gigabitethernet 0/0/2
[SwitchC-GigabitEthernet0/0/2] stp edged-port enable
[SwitchC-GigabitEthernet0/0/2] quit
```
    (Optional) Configure BPDU protection on SwitchC.
```
[SwitchC] stp bpdu-protection
```
    If edge ports are connected to network devices that have STP enabled and BPDU protection is enabled, the edge ports will be shut down and their attributes remain unchanged after they receive BPDUs.
  - Enable RSTP globally.
    
    # Enable RSTP globally on SwitchA.
```
[SwitchA] stp enable
```
    # Enable RSTP globally on SwitchB.
```
[SwitchB] stp enable
```
    # Enable RSTP globally on SwitchC.
```
[SwitchC] stp enable
```
    # Enable RSTP globally on SwitchD.
```
[SwitchD] stp enable
```

Configure RSTP protection functions. For example, configure root protection on designated ports of the root bridge.

# Enable root protection on GE0/0/1 on SwitchA.

[SwitchA] interface gigabitethernet 0/0/1
[SwitchA-GigabitEthernet0/0/1] stp root-protection
[SwitchA-GigabitEthernet0/0/1] quit

# Enable root protection on GE0/0/2 on SwitchA.

[SwitchA] interface gigabitethernet 0/0/2
[SwitchA-GigabitEthernet0/0/2] stp root-protection
[SwitchA-GigabitEthernet0/0/2] quit

Verify the configuration.
After the preceding configuration is complete and the network becomes stable, perform the following operations to verify the configuration.

# Run the display stp brief command on SwitchA to check the port roles and states.
```
[SwitchA] display stp brief
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        DESI  FORWARDING      ROOT
   0    GigabitEthernet0/0/2        DESI  FORWARDING      ROOT
```
After SwitchA is configured as the root bridge, GigabitEthernet0/0/2 connected to SwitchB and GigabitEthernet0/0/1 connected to SwitchD are elected as designated ports through spanning tree calculation. Root protection is enabled on the designated ports.

# Run the display stp interface gigabitethernet 0/0/1 brief command on SwitchB to check the role and state of GigabitEthernet0/0/1.
```
[SwitchB] display stp interface gigabitethernet 0/0/1 brief
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        DESI  FORWARDING      NONE      
```
GigabitEthernet0/0/1 is elected as a designated port and is in Forwarding state.

# Run the display stp brief command on SwitchC to check the port roles and states.
```
[SwitchC] display stp brief
 MSTID  Port                        Role  STP State     Protection
   0    GigabitEthernet0/0/1        ALTE  DISCARDING      NONE     
   0    GigabitEthernet0/0/2        DESI  FORWARDING      BPDU     
   0    GigabitEthernet0/0/3        ROOT  FORWARDING      NONE     
```
GE0/0/1 is elected as an alternate port and is in Discarding state.

GE0/0/3 is elected as a root port and is in Forwarding state.

Configuration Files

SwitchA configuration file

#
sysname SwitchA                             
#                                
stp mode rstp                   
stp instance 0 root primary     
stp pathcost-standard legacy
#                                
interface GigabitEthernet0/0/1   
 stp root-protection             
#                                
interface GigabitEthernet0/0/2   
 stp root-protection             
#
return

SwitchB configuration file

#                                
sysname SwitchB               
#                                
stp mode rstp                   
stp bpdu-protection
stp pathcost-standard legacy
#                             
interface GigabitEthernet0/0/2        
 stp edged-port enable
#                                
return

SwitchC configuration file

#                                
sysname SwitchC                                   
#                                
stp mode rstp                   
stp bpdu-protection
stp pathcost-standard legacy
#                                
interface GigabitEthernet0/0/1       
 stp instance 0 cost 20000       
#                                
interface GigabitEthernet0/0/2        
 stp edged-port enable
#                                
return

SwitchD configuration file

#                                
sysname SwitchD                               
#                                
stp mode rstp                   
stp instance 0 root secondary   
stp pathcost-standard legacy
#                                
return

Example for Configuring RSTP

Networking Requirements

Configuration Roadmap

Procedure

Configuration Files

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