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Example: Configuring Faster Convergence and Improving Network Stability with RSTP

Requirements

• Junos OS Release 11.1 for the QFX3500 switches
• Four QFX3500 switches

Overview and Topology

In this example, QFX3500 switches are connected in the topology displayed in Figure 1 to create a loop-free topology.

Figure 1: Network Topology for RSTP

The interfaces shown in Table 1 will be configured for RSTP.

Note: You can configure RSTP on logical or physical interfaces. This example shows RSTP configured on logical interfaces.

This configuration example creates a loop-free topology between four switches using RSTP.

An RSTP topology contains ports that have specific roles:

• The root port is responsible for forwarding data to the root bridge.
• The alternate port is a standby port for the root port. When a root port goes down, the alternate port becomes the active root port.
• The designated port forwards data to the downstream network segment or device.
• The backup port is a backup port for the designated port. When a designated port goes down, the backup port becomes the active designated port and starts forwarding data.

Configuring RSTP on Switch 1

CLI Quick Configuration

To quickly configure interfaces and RSTP on Switch 1, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs sales-vlan, engineering-vlan and publications-vlan, and support-vlan:
   [edit vlans]
user@switch1# set sales-vlan description “Sales VLAN”
user@switch1# set sales-vlan vlan-id 10
user@switch1# set engineering-vlan description “Engineering VLAN”
user@switch1# set engineering-vlan vlan-id 20
user@switch1# set publications-vlan description “Publications VLAN”
user@switch1# set publications-vlan vlan-id 30

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch1# set xe-0/0/13 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch1# set xe-0/0/9 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch1# set xe-0/0/11 unit 0 family ethernet-switching vlan members [10 20 30 40]

3. Configure the port mode for the interfaces:
   [edit interfaces]
user@switch1# set xe-0/0/13 unit 0 family ethernet-switching port-mode trunk
user@switch1# set xe-0/0/9 unit 0 family ethernet-switching port-mode trunk
user@switch1# set xe-0/0/11 unit 0 family ethernet-switching port-mode trunk
4. Configure RSTP on the switch:
   [edit protocols]

user@switch1# rstp bridge-priority 16k
user@switch1# rstp interface xe-0/0/13.0 cost 1000
user@switch1# rstp interface xe-0/0/13.0 mode point-to-point
user@switch1# rstp interface xe-0/0/9.0 cost 1000
user@switch1# rstp interface xe-0/0/9.0 mode point-to-point
user@switch1# rstp interface xe-0/0/11.0 cost 1000
user@switch1# rstp interface xe-0/0/11.0 mode point-to-point

   
   

Results

Check the results of the configuration:

Configuring RSTP on Switch 2

CLI Quick Configuration

To quickly configure interfaces and RSTP on Switch 2, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs sales-vlan, engineering-vlan and publications-vlan, and support-vlan:
   [edit vlans]
user@switch2# set sales-vlan description “Sales VLAN”
user@switch2# set sales-vlan vlan-id 10
user@switch2# set engineering-vlan description “Engineering VLAN”
user@switch2# set engineering-vlan vlan-id 20
user@switch2# set publications-vlan description “Publications VLAN”
user@switch2# set publications-vlan vlan-id 30
user@switch2# set support-vlan vlan-description “Support VLAN”
user@switch2# set publications-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch2# set xe-0/0/14 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch2# set xe-0/0/18 unit 0 family ethernet-switching vlan members [10 20 30 40]

3. Configure the port mode for the interfaces:
   [edit interfaces]
user@switch2# set xe-0/0/14 unit 0 family ethernet-switching port-mode trunk
user@switch2# set xe-0/0/18 unit 0 family ethernet-switching port-mode trunk

   
   
4. Configure RSTP on the switch:
   [edit protocols]
user@switch2# rstp bridge-priority 32k
user@switch2# rstp interface xe-0/0/14.0 cost 1000
user@switch2# rstp interface xe-0/0/14.0 mode point-to-point
user@switch2# rstp interface xe-0/0/18.0 cost 1000
user@switch2# rstp interface xe-0/0/18.0 mode point-to-point


Results

Check the results of the configuration:

Configuring RSTP on Switch 3

CLI Quick Configuration

To quickly configure interfaces and RSTP on Switch 3, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs sales-vlan, engineering-vlan, publications-vlan, and support-vlan:
   [edit vlans]
user@switch3# set sales-vlan description “Sales VLAN”
user@switch3# set sales-vlan vlan-id 10
user@switch3# set engineering-vlan description “Engineering VLAN”
user@switch3# set engineering-vlan vlan-id 20
user@switch3# set publications-vlan description “Publications VLAN”
user@switch3# set publications-vlan vlan-id 30
user@switch3# set support-vlan description “Support VLAN”
user@switch3# set publications-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch3# set xe-0/0/26 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch3# set xe-0/0/28 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch3# set xe-0/0/24 unit 0 family ethernet-switching vlan members [10 20 30 40]

3. Configure the port mode for the interfaces:
   [edit interfaces]
user@switch3# set xe-0/0/26 unit 0 family ethernet-switching port-mode trunk
user@switch3# set xe-0/0/28 unit 0 family ethernet-switching port-mode trunk
user@switch3# set xe-0/0/24 unit 0 family ethernet-switching port-mode trunk
4. Configure RSTP on the switch:
   [edit protocols]
user@switch3# rstp bridge-priority 8k
user@switch3# rstp interface xe-0/0/26.0 cost 1000
user@switch3# rstp interface xe-0/0/26.0 mode point-to-point
user@switch3# rstp interface xe-0/0/28.0 cost 1000
user@switch3# rstp interface xe-0/0/28.0 mode point-to-point
user@switch3# rstp interface xe-0/0/24.0 cost 1000
user@switch3# rstp interface xe-0/0/24.0 mode point-to-point

   
   

Results

Check the results of the configuration:

Configuring RSTP on Switch 4

CLI Quick Configuration

To quickly configure interfaces and RSTP on Switch 4, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs sales-vlan, engineering-vlan, publications-vlan, and support-vlan:
   [edit vlans]
user@switch4# set sales-vlan description “Sales VLAN”
user@switch4# set sales-vlan vlan-id 10
user@switch4# set engineering-vlan description “Engineering VLAN”
user@switch4# set engineering-vlan vlan-id 20
user@switch4# set publications-vlan description “Publications VLAN”
user@switch4# set publications-vlan vlan-id 30
user@switch4# set support-vlan description “Support VLAN”
user@switch4# set publications-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch4# set xe-0/0/23 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch4# set xe-0/0/19 unit 0 family ethernet-switching vlan members [10 20 30 40]

3. Configure the port mode for the interfaces:
   [edit interfaces]
user@switch4# set xe-0/0/23 unit 0 family ethernet-switching port-mode trunk
user@switch4# set xe-0/0/19 unit 0 family ethernet-switching port-mode trunk
4. Configure RSTP on the switch:
   [edit protocols]
user@switch4# rstp bridge-priority 16k
user@switch4# rstp interface all cost 1000
user@switch4# rstp interface xe-0/0/23.0 cost 1000
user@switch4# rstp interface xe-0/0/23.0 mode point-to-point
user@switch4# rstp interface xe-0/0/19.0 cost 1000
user@switch4# rstp interface xe-0/0/19.0 mode point-to-point

   
   

Results

Check the results of the configuration:

Verification

To confirm that the configuration is working properly, perform these tasks:

• Verifying RSTP Configuration on Switch 1
• Verifying RSTP Configuration on Switch 2
• Verifying RSTP Configuration on Switch 3
• Verifying RSTP Configuration on Switch 4

Verifying RSTP Configuration on Switch 1

Purpose

Verify that the RSTP configuration on Switch 1 is correct.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
xe-0/0/13.0    128:527      128:525  16384.0019e25040e0      1000  BLK    ALT 
xe-0/0/9.0     128:529      128:513  32768.0019e2503d20      1000  BLK    ALT  
xe-0/0/11.0    128:531      128:513   8192.0019e25051e0      1000  FWD    ROOT  

Meaning

See the topology in Figure 1. The operational mode command show spanning-tree interface shows that xe-0/0/13.0 is in a forwarding state. The other interfaces on Switch 1 are blocked.

Verifying RSTP Configuration on Switch 2

Purpose

Verify that the RSTP configuration on Switch 2 is correct.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
xe-0/0/14.0     128:513      128:513  32768.0019e2503d20      1000  BLK    DESG 
xe-0/0/18.0     128:519      128:515   8192.0019e25051e0      1000  FWD    ROOT 

Meaning

See the topology in Figure 1. The operational mode command show spanning-tree interface shows that interface xe-0/0/18.0 is in a forwarding state and the root port. The other interface on Switch 2 is blocked.

Verifying RSTP Configuration on Switch 3

Purpose

Verify that the RSTP configuration on Switch 3 is correct.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
xe-0/0/26.0     128:513      128:513   8192.0019e25051e0      1000  FWD    DESG 
xe-0/0/28.0     128:515      128:515   8192.0019e25051e0      1000  FWD    DESG 
xe-0/0/24.0     128:517      128:517   8192.0019e25051e0      1000  FWD    DESG 

Meaning

See the topology in Figure 1. The operational mode command show spanning-tree interface shows that no interface is the root interface.

Verifying RSTP Configuration on Switch 4

Purpose

Verify the RSTP configuration on Switch 4.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost

xe-0/0/23.0    128:523      128:517   8192.0019e25051e0      1000  FWD    ROOT 
xe-0/0/19.0    128:525      128:525  16384.0019e25040e0      1000  FWD    DESG 

Meaning

See the topology in Figure 1. The operational mode command show spanning-tree interface shows that interface xe-0/0/23.0 is the root interface and is in the forwarding state.