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Example: Faster Convergence and Improved Network Stability with RSTP on EX Series Switches

Requirements

• Junos OS Release 11.3 or later for EX Series switches
• Four EX Series switches

• Installed the four switches. See Connecting and Configuring an EX Series Switch (J-Web Procedure).
• Performed the initial software configuration on all switches. See Installing and Connecting an EX3200 Switch.

Overview and Topology

RSTP works by identifying certain links as point to point links and blocking other possible paths. When one of the point-to-point links fails, a designated alternate link transitions to the forwarding state and take over. Configuring nonstop bridging (NSB) on a switch with redundant Routing Engines keeps RSTP synchronized on both Routing Engines. This way, RSTP remains active immediately after a switchover because it is already synchronized to the backup Routing Engine. RSTP does not have to reconverge after a Routing Engine switchover when NSB is enabled because the neighbor devices do not detect an RSTP change on the switch. In this example, four EX Series switches are connected in the topology displayed in Figure 1 to create a loop-free topology with NSB applied to switches with dual Routing Engines.

Figure 1: Network Topology for RSTP

Table 1 shows the components of the topology for this example.

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 EX Series 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.

Note: You also can create a loop-free topology between the aggregation layer and the distribution layer using redundant trunk links. For more information about configuring redundant trunk links, see Example: Configuring Redundant Trunk Links for Faster Recovery.

Configuring RSTP and Nonstop Bridging on Switch 1

CLI Quick Configuration

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

If Switch 1 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 1, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:
   [edit vlans]
user@switch1# set voice-vlan description “Voice VLAN”
user@switch1# set voice-vlan vlan-id 10
user@switch1# set employee-vlan description “Employee VLAN”
user@switch1# set employee-vlan vlan-id 20
user@switch1# set guest-vlan description “Guest VLAN”
user@switch1# set guest-vlan vlan-id 30
user@switch1# set camera-vlan description “Camera VLAN”
user@switch1# set camera-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch1# set ge-0/0/13 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch1# set ge-0/0/9 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch1# set ge-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 ge-0/0/13 unit 0 family ethernet-switching port-mode trunk
user@switch1# set ge-0/0/9 unit 0 family ethernet-switching port-mode trunk
user@switch1# set ge-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 ge-0/0/13.0 cost 1000
user@switch1# rstp interface ge-0/0/13.0 mode point-to-point
user@switch1# rstp interface ge-0/0/9.0 cost 1000
user@switch1# rstp interface ge-0/0/9.0 mode point-to-point
user@switch1# rstp interface ge-0/0/11.0 cost 1000
user@switch1# rstp interface ge-0/0/11.0 mode point-to-point

   
   

Step-by-Step Procedure

1. Enable graceful Routing Engine switchover (GRES):
   [edit chassis redundancy]
user@switch1# set graceful-switchover
2. Configure the switch to always synchronize configuration changes between the Routing Engines:
   [edit system]
user@switch1# set commit synchronize

   If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

3. Enable nonstop bridging:
   [edit ethernet-switching-options]
user@switch1# set nonstop-bridging

   Note: This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 2

CLI Quick Configuration

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

If Switch 2 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 2, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:
   [edit vlans]
user@switch2# set voice-vlan description “Voice VLAN”
user@switch2# set voice-vlan vlan-id 10
user@switch2# set employee-vlan description “Employee VLAN”
user@switch2# set employee-vlan vlan-id 20
user@switch2# set guest-vlan description “Guest VLAN”
user@switch2# set guest-vlan vlan-id 30
user@switch2# set camera-vlan vlan-description “Camera VLAN”
user@switch2# set camera-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch2# set ge-0/0/14 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch2# set ge-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 ge-0/0/14 unit 0 family ethernet-switching port-mode trunk
user@switch2# set ge-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 ge-0/0/14.0 cost 1000
user@switch2# rstp interface ge-0/0/14.0 mode point-to-point
user@switch2# rstp interface ge-0/0/18.0 cost 1000
user@switch2# rstp interface ge-0/0/18.0 mode point-to-point


Step-by-Step Procedure

1. Enable graceful Routing Engine switchover (GRES):
   [edit chassis redundancy]
user@switch2# set graceful-switchover
2. Configure the switch to always synchronize configuration changes between the Routing Engines:
   [edit system]
user@switch2# set commit synchronize

   If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

3. Enable nonstop bridging:
   [edit ethernet-switching-options]
user@switch2# set nonstop-bridging

   Note: This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 3

CLI Quick Configuration

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

If Switch 3 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 3, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:
   [edit vlans]
user@switch3# set voice-vlan description “Voice VLAN”
user@switch3# set voice-vlan vlan-id 10
user@switch3# set employee-vlan description “Employee VLAN”
user@switch3# set employee-vlan vlan-id 20
user@switch3# set guest-vlan description “Guest VLAN”
user@switch3# set guest-vlan vlan-id 30
user@switch3# set camera-vlan description “Camera VLAN”
user@switch3# set camera-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch3# set ge-0/0/26 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch3# set ge-0/0/28 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch3# set ge-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 ge-0/0/26 unit 0 family ethernet-switching port-mode trunk
user@switch3# set ge-0/0/28 unit 0 family ethernet-switching port-mode trunk
user@switch3# set ge-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 ge-0/0/26.0 cost 1000
user@switch3# rstp interface ge-0/0/26.0 mode point-to-point
user@switch3# rstp interface ge-0/0/28.0 cost 1000
user@switch3# rstp interface ge-0/0/28.0 mode point-to-point
user@switch3# rstp interface ge-0/0/24.0 cost 1000
user@switch3# rstp interface ge-0/0/24.0 mode point-to-point

   
   

Step-by-Step Procedure

1. Enable graceful Routing Engine switchover (GRES):
   [edit chassis redundancy]
user@switch3# set graceful-switchover
2. Configure the switch to always synchronize configuration changes between the Routing Engines:
   [edit system]
user@switch3# set commit synchronize

   If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

3. Enable nonstop bridging:
   [edit ethernet-switching-options]
user@switch3# set nonstop-bridging

   Note: This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Configuring RSTP and Nonstop Bridging on Switch 4

CLI Quick Configuration

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

If Switch 4 includes dual Routing Engines, configure NSB. To quickly configure nonstop bridging on Switch 4, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Configure the VLANs voice-vlan, employee-vlan, guest-vlan, and camera-vlan:
   [edit vlans]
user@switch4# set voice-vlan description “Voice VLAN”
user@switch4# set voice-vlan vlan-id 10
user@switch4# set employee-vlan description “Employee VLAN”
user@switch4# set employee-vlan vlan-id 20
user@switch4# set guest-vlan description “Guest VLAN”
user@switch4# set guest-vlan vlan-id 30
user@switch4# set camera-vlan description “Camera VLAN”
user@switch4# set camera-vlan vlan-id 40

2. Configure the VLANs on the interfaces, including support for the Ethernet switching protocol:
   [edit interfaces]
user@switch4# set ge-0/0/23 unit 0 family ethernet-switching vlan members [10 20 30 40]
user@switch4# set ge-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 ge-0/0/23 unit 0 family ethernet-switching port-mode trunk
user@switch4# set ge-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 ge-0/0/23.0 cost 1000
user@switch4# rstp interface ge-0/0/23.0 mode point-to-point
user@switch4# rstp interface ge-0/0/19.0 cost 1000
user@switch4# rstp interface ge-0/0/19.0 mode point-to-point

   
   

Step-by-Step Procedure

1. Enable graceful Routing Engine switchover (GRES):
   [edit chassis redundancy]
user@switch4# set graceful-switchover
2. Configure the switch to always synchronize configuration changes between the Routing Engines:
   [edit system]
user@switch4# set commit synchronize

   If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

3. Enable nonstop bridging:
   [edit ethernet-switching-options]
user@switch4# set nonstop-bridging

   Note: This process enables NSB for all NSB-supported Layer 2 protocols on the switch, including RSTP.

Results

Check the results of the configuration:

Verification

To confirm that the configuration is working properly, perform these tasks on both Routing Engines:

• 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 the RSTP configuration on Switch 1.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/0/13.0    128:526      128:526  16384.0019e25040e0      1000  BLK    ALT 
ge-0/0/9.0     128:522      128:522  32768.0019e2503d20      1000  BLK    ALT  
ge-0/0/11.0    128:524      128:524   8192.0019e25051e0      1000  FWD    ROOT  

Meaning

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

Verifying RSTP Configuration on Switch 2

Purpose

Use this procedure to verify the RSTP configuration on both Switch 2 Routing Engines.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/0/14.0     128:527      128:527  32768.0019e2503d20      1000  FWD    DESG 
ge-0/0/18.0     128:529      128:529   8192.0019e25051e0      1000  FWD    ROOT 

Meaning

Refer to the topology in Figure 1. The operational mode command show spanning-tree interface shows that ge-0/0/18.0 is in a forwarding state and is the root port.

Verifying RSTP Configuration on Switch 3

Purpose

Use this procedure to verify the RSTP configuration on both Switch 3 Routing Engines.

Action

Spanning tree interface parameters for instance 0

Interface    Port ID    Designated      Designated         Port    State  Role
                         port ID        bridge ID          Cost
ge-0/0/26.0     128:539      128:539   8192.0019e25051e0      1000  FWD    DESG 
ge-0/0/28.0     128:541      128:541   8192.0019e25051e0      1000  FWD    DESG 
ge-0/0/24.0     128:537      128:537   8192.0019e25051e0      1000  FWD    DESG 

Meaning

Refer to 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

Use this procedure to verify the RSTP configuration on both Switch 4 Routing Engines.

Action

Spanning tree interface parameters for instance 0

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

ge-0/0/23.0    128:536      128:536   8192.0019e25051e0      1000  FWD    ROOT 
ge-0/0/19.0    128:532      128:532   16384.0019e25040e0     1000  FWD    DESG 

Meaning

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