RPVST+ scenario

In this scenario, four switches are interconnected. VLANs 10 and 20 are defined on all switches, causing a network loop.

To eliminate the loop, RPVST+ is enabled and switch A and B are defined as high-priority for VLAN 10 and 20 respectively. RPVST+ then eliminates the loop by assigning switch A as the root for VLAN 10 and switch B designated as the root for VLAN 20, and blocking access on one of the links.

Procedure
  1. Configure switch A.
    1. Create VLANs 1, 10, and 20. 
      switch# config
switch(config)# vlan 1, 10, 20
    2. Enable RPVST+ and assign the VLANs 10 and 20 to it. Assign a priority of 5 to VLAN 10. This will force switch A to become the root of the spanning tree for VLAN 10. 
      switch(config)# spanning-tree mode rpvst
switch(config)# spanning-tree
switch(config)# spanning-tree vlan 10,20
switch(config)# spanning-tree vlan 10 priority 5
    3. Define interfaces 1/1/1 and 1/1/2. 
      switch(config)# interface 1/1/1
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all
switch(config-if)# interface 1/1/2
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all
  2. Configure switch B and switch C with the same settings.
    1. Create VLANs 1, 10, and 20. 
      switch# config
switch(config)# vlan 1, 10, 20
    2. Enable RPVST+ and assign the VLANs 10 and 20 to it. 
      switch(config)# spanning-tree mode rpvst
switch(config)# spanning-tree
switch(config)# spanning-tree vlan 10,20
    3. Define interfaces 1/1/1 and 1/1/2. 
      switch(config)# interface 1/1/1
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all
switch(config-if)# interface 1/1/2
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all
  3. Configure switch D.
    1. Create VLANs 1, 10, and 20. 
      switch# config
switch(config)# vlan 1, 10, 20
    2. Enable RPVST+ and assign the VLANs 10 and 20 to it. Assign a priority of 5 to VLAN 20. This will force switch D to become the root of the spanning tree for VLAN 20. 
      switch(config)# spanning-tree mode rpvst
switch(config)# spanning-tree
switch(config)# spanning-tree vlan 10,20
switch(config)# spanning-tree vlan 20 priority 5
    3. Define interfaces 1/1/1 and 1/1/2. 
      switch(config)# interface 1/1/1
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all
switch(config-if)# interface 1/1/2
switch(config-if)# no shutdown
switch(config-if)# no routing
switch(config-if)# vlan trunk native 1
switch(config-if)# vlan trunk allowed all