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    Example: Configuring Faster Convergence and Improving Network Stability with RSTP

    The QFX Series products use Rapid Spanning Tree Protocol (RSTP) to provide a loop-free topology. RSTP identifies certain links as point to point. When a point-to-point link fails, the alternate link can transition to the forwarding state. RSTP provides quicker reconvergence time than original STP because it uses protocol handshake messages rather than fixed timeouts. Eliminating the need to wait for timers to expire makes RSTP more efficient than STP.

    This example describes how to configure RSTP on four QFX3500 switches:

    Requirements

    This example uses the following hardware and software components:

    • 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

    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.

    Table 1: Topology for Configuring RSTP on the QFX Series

    Components

    Settings

    Switch 1

    The following ports on Switch 1 are connected in this way:

    • xe-0/0/9 is connected to Switch 2
    • xe-0/0/13 is connected to Switch 4
    • xe-0/0/11 is connected to Switch 3

    Switch 2

    The following ports on Switch 2 are connected in this way:

    • xe-0/0/14 is connected to Switch 1
    • xe-0/0/18 is connected to Switch 3

    Switch 3

    The following ports on Switch 3 are connected in this way:

    • xe-0/0/26 is connected to Switch 1
    • xe-0/0/28 is connected to Switch 2
    • xe-0/0/24 is connected to Switch 4

    Switch 4

    The following ports on Switch 4 are connected in this way:

    • xe-0/0/19 is connected to Switch 1
    • xe-0/0/23 is connected to Switch 3

    VLAN names and tag IDs

    sales-vlan, tag 10
    engineering-vlan, tag 20
    publications-vlan, tag 30
    support-vlan, tag 40

    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:

    Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

    [edit]

    set vlans sales-vlan description “Sales VLAN”

    set vlans sales-vlan vlan-id 10

    set vlans engineering-vlan description “Engineering VLAN”

    set vlans engineering-vlan vlan-id 20

    set vlans publications-vlan description “Publications VLAN”

    set vlans publications-vlan vlan-id 30

    set vlans support-vlan description “Support VLAN”

    set vlans support-vlan vlan-id 40

    set interfaces xe-0/0/13 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/9 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/11 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/13 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/9 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/11 unit 0 family ethernet-switching port-mode trunk

    set protocols rstp bridge-priority 16k

    set protocols rstp interface xe-0/0/13.0 cost 1000

    set protocols rstp interface xe-0/0/13.0 mode point-to-point

    set protocols rstp interface xe-0/0/9.0 cost 1000

    set protocols rstp interface xe-0/0/9.0 mode point-to-point

    set protocols rstp interface xe-0/0/11.0 cost 1000

    set protocols rstp interface xe-0/0/11.0 mode point-to-point

    Step-by-Step Procedure

    To configure interfaces and RSTP on Switch 1:

    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:

      Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

      [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:

    user@switch1> show configuration
    interfaces {xe-0/0/13 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/9 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/11 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}}
    protocols {rstp {bridge-priority 16k;interface xe-0/0/13.0 {cost 1000;mode point-to-point;}interface xe-0/0/9.0 {cost 1000;mode point-to-point;}interface xe-0/0/11.0 {cost 1000;mode point-to-point;}}}}
    vlans {sales-vlan {vlan-id 10;}engineering-vlan {vlan-id 20;}publications-vlan {vlan-id 30;}support-vlan {vlan-id 40;}}

    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:

    Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

    [edit]

    set vlans sales-vlan description “Sales VLAN”

    set vlans sales-vlan vlan-id 10

    set vlans engineering-vlan description “Engineering VLAN”

    set vlans engineering-vlan vlan-id 20

    set vlans publications-vlan description “Publications VLAN”

    set vlans publications-vlan vlan-id 30

    set vlans support-vlan description “Support VLAN”

    set vlans support-vlan vlan-id 40

    set interfaces xe-0/0/14 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/18 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/14 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/18 unit 0 family ethernet-switching port-mode trunk

    set protocols rstp bridge-priority 32k

    set protocols rstp interface xe-0/0/14.0 cost 1000

    set protocols rstp interface xe-0/0/14.0 mode point-to-point

    set protocols rstp interface xe-0/0/18.0 cost 1000

    set protocols rstp interface xe-0/0/18.0 mode point-to-point

    Step-by-Step Procedure

    To configure interfaces and RSTP on Switch 2:

    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:

      Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

      [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:

    user@switch2> show configuration
    interfaces {xe-0/0/14 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/18 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}}
    protocols {rstp {bridge-priority 32k;interface xe-0/0/14.0 {cost 1000;mode point-to-point;}interface xe-0/0/18.0 {cost 1000;mode point-to-point;}}}}
    vlans {sales-vlan {vlan-id 10;}engineering-vlan {vlan-id 20;}publications-vlan {vlan-id 30;}support-vlan {vlan-id 40;}}

    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:

    Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

    [edit]

    set vlans sales-vlan description “Sales VLAN”

    set vlans sales-vlan vlan-id 10

    set vlans engineering-vlan description “Engineering VLAN”

    set vlans engineering-vlan vlan-id 20

    set vlans publications-vlan description “Publications VLAN”

    set vlans publications-vlan vlan-id 30

    set vlans support-vlan description “Support VLAN”

    set vlans support-vlan vlan-id 40

    set interfaces xe-0/0/26 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/28 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/24 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/26 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/28 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/24 unit 0 family ethernet-switching port-mode trunk

    set protocols rstp bridge-priority 8k

    set protocols rstp interface xe-0/0/26.0 cost 1000

    set protocols rstp interface xe-0/0/26.0 mode point-to-point

    set protocols rstp interface xe-0/0/28.0 cost 1000

    set protocols rstp interface xe-0/0/28.0 mode point-to-point

    set protocols rstp interface xe-0/0/24.0 cost 1000

    set protocols rstp interface xe-0/0/24.0 mode point-to-point

    Step-by-Step Procedure

    To configure interfaces and RSTP on Switch 3:

    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:

      Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

      [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:

    user@switch3> show configuration
    interfaces {xe-0/0/26 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/28 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/24 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}}}
    protocols {rstp {bridge-priority 8k;interface xe-0/0/26.0 {cost 1000;mode point-to-point;}interface xe-0/0/28.0 {cost 1000;mode point-to-point;}interface xe-0/0/24.0 {cost 1000;mode point-to-point;}}bridge-priority 8k;}}}}
    vlans {sales-vlan {vlan-id 10;}engineering-vlan {vlan-id 20;}publications-vlan {vlan-id 30;}support-vlan {vlan-id 40;}}

    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:

    Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

    [edit]

    set vlans sales-vlan description “Sales VLAN”

    set vlans sales-vlan vlan–id 10

    set vlans engineering-vlan description “Engineering VLAN”

    set vlans engineering-vlan vlan-id 20

    set vlans publications-vlan description “Publications VLAN”

    set vlans publications-vlan vlan-id 30

    set vlans support-vlan description “Support VLAN”

    set vlans support-vlan vlan-id 40

    set interfaces xe-0/0/23 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/19 unit 0 family ethernet-switching vlan members [10 20 30 40]

    set interfaces xe-0/0/23 unit 0 family ethernet-switching port-mode trunk

    set interfaces xe-0/0/19 unit 0 family ethernet-switching port-mode trunk

    set protocols rstp bridge-priority 16k

    set protocols rstp interface xe-0/0/23.0 cost 1000

    set protocols rstp interface xe-0/0/23.0 mode point-to-point

    set protocols rstp interface xe-0/0/19.0 cost 1000

    set protocols rstp interface xe-0/0/19.0 mode point-to-point

    Step-by-Step Procedure

    To configure interfaces and RSTP on Switch 4:

    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:

      Note: If you are configuring RSTP on devices that support the Enhanced Layer 2 Switching (ELS) CLI, use the interface-mode statement instead of the port-mode statement. The port-mode statement has been replaced with the interface-mode statement.

      [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:

    user@switch4> show configuration
    interfaces {xe-0/0/23 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}xe-0/0/19 {unit 0 {family ethernet-switching {port-mode trunk;vlan {members [10 20 30 40];}}}}}
    protocols {rstp {bridge-priority 16k;interface xe-0/0/23.0 {cost 1000;mode point-to-point;}interface xe-0/0/19.0 {cost 1000;mode point-to-point;}}}}
    vlans {sales-vlan {vlan-id 10;}engineering-vlan {vlan-id 20;}publications-vlan {vlan-id 30;}support-vlan {vlan-id 40;}}

    Verification

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

    Verifying RSTP Configuration on Switch 1

    Purpose

    Verify that the RSTP configuration on Switch 1 is correct.

    Action

    In operational mode, issue the show spanning-tree interface command:

    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

    In operational mode issue the show spanning-tree interface command:

    
    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

    In operational mode, issue the show spanning-tree interface command:

    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

    In operational mode, issue the show spanning-tree interface command:

    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.

    Modified: 2016-11-16