Configuring Interop Feature 802.1W

Interop feature with 802.1W can be configured on an interface in RSTP mode. Interop feature helps the 802.1D RSTP port to be compatible with 802.1W. This is configured on a port which is Point-to-Point link type.

Parent topic: Configuration of Spanning Tree Guard

Sample Configuration of Loop Guard on an Interface (in RSTP)

  1. Following is a sample configuration for enabling Interop feature (802.1W) in RSTP in an interface:

    Type the following:

    iS5comm# configure terminal
    iS5comm(config)# interface gigabitethernet 0/2
    iS5comm(config-if)#no shutdown 
    iS5comm(config-if)#end
    iS5comm# configure terminal
    iS5comm(config)# spanning-tree mode rst
    Spanning Tree protocol enabled is MST. Now MST is being shutdown and RST is being enabled
    iS5comm(config)# end
    iS5comm# configure terminal
    iS5comm(config)# interface gigabitethernet 0/1
    iS5comm(config-if)# spanning-tree link-type point-to-point
    iS5comm(config-if)# spanning-tree mode dot1w enable
    iS5comm(config-if)# end
    • Verify the 802.1W mode using the show command given below.
    iS5comm# show spanning-tree interface gigabitethernet 0/2 detail
    Port 1 [Gi0/1] is Disabled  , Discarding
    Port PathCost 200000, Port Priority 128, Port Identifier  128.1
    Designated Root has priority 0, address 00:00:00:00:00:00
    Designated Bridge has priority 0, address 00:00:00:00:00:00
    Designated Port Id is 0.0, Designated PathCost 0
    No of Transitions to forwarding State :0
    Auto-Edge is enabled
    PortFast is disabled, Oper-Edge is disabled
    Link Type is Shared
    BPDUs : sent 0 , received 0
    Timers: Hello - 0, Forward Delay - 0, Topology Change - 0,
    Error Disable Recovery Interval 300 sec 0 cs
    Restricted Role is disabled.
    Restricted TCN is disabled.
    bpdu-transmit enabled
    bpdu-receive enabled
    Root Guard is disabled.
    Loop Guard is disabled.
    Dot1W mode enabled.
    • In packet capture, verify that the path cost, port ID, Bridge Priority, and Bridge ID MAC address are based on the Port priority vector instead of designated priority vector.
    iS5comm# show spanning-tree
    Spanning tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x78 (Agreement, Forwarding, Learning, Port Role: Root)
    0... .... = Topology Change Acknowledgment: No
    .1.. .... = Agreement: Yes
    ..1. .... = Forwarding: Yes
    ...1 .... = Learning: Yes
    .... 10.. = Port Role: Root (2)
    .... ..0. = Proposal: No
    .... ...0 = Topology Change: No
    Root Identifier: 32768 / 0 / 00:01:02:03:04:01
    Root Bridge Priority: 32768
    Root Bridge System ID Extension: 0
    Root Bridge System ID: 00:01:02:03:04:01
    Root Path Cost: 0
    Bridge Identifier: 32768 / 0 / 00:01:02:03:04:01
    Bridge Priority: 32768
    Bridge System ID Extension: 0
    Bridge System ID: 00:01:02:03:04:01
    

    Dot1w Disable:
    

    2. 

  2. Following is a sample configuration for enabling Interop
feature (802.1W) in RSTP in an interface:

    Type the following:
    

    iS5comm# configure terminal
    iS5comm(config)# interface gigabitethernet 0/1
    iS5comm(config-if)# spanning-tree mode dot1w disable 
    iS5comm(config)# end
      

    • Verify the 802.1W mode
using the show command given below.
      • 

    

    iS5comm# show spanning-tree interface gigabitethernet 0/1 detail
    Port 1 [Gi0/1] is Disabled  , Discarding
    

    Port PathCost 200000, Port Priority 128, Port Identifier  128.1
    

    Designated Root has priority 0, address 00:00:00:00:00:00
    

    Designated Bridge has priority 0, address 00:00:00:00:00:00
    

    Designated Port Id is 0.0, Designated PathCost 0
    

    No of Transitions to forwarding State :0
    

    Auto-Edge is enabled
    

    PortFast is disabled, Oper-Edge is disabled
    

    Link Type is Shared
    

    BPDUs : sent 0 , received 0
    

    Timers: Hello - 0, Forward Delay - 0, Topology Change - 0,
    

    Error Disable Recovery Interval 300 sec 0 cs
    

    Restricted Role is disabled.
    

    Restricted TCN is disabled.
    

    bpdu-transmit enabled
    

    bpdu-receive enabled
    

    Root Guard is disabled.
    

    Loop Guard is disabled.
    

    Dot1W mode disabled.
    

      

    • In packet capture, verify that the path cost, port ID, Bridge
Priority, and Bridge ID MAC address
are based on the designated priority vector.
      • 

    

    iS5comm# show spanning-tree
    Spanning tree Protocol
    

    Protocol Identifier: Spanning Tree Protocol (0x0000)
    

    Protocol Version Identifier: Rapid Spanning Tree (2)
    

    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    

    BPDU flags: 0x78 (Agreement, Forwarding, Learning, Port Role: Root)
    

    0... .... = Topology Change Acknowledgment: No
    

    .1.. .... = Agreement: Yes
    

    ..1. .... = Forwarding: Yes
    

    ...1 .... = Learning: Yes
    

    .... 10.. = Port Role: Root (2)
    

    .... ..0. = Proposal: No
    

    .... ...0 = Topology Change: No
    

    Root Identifier: 32768 / 0 / 00:01:02:03:04:01
    

    Root Bridge Priority: 32768
    

    Root Bridge System ID Extension: 0
    

    Root Bridge System ID: 00:01:02:03:04:01
    

    Root Path Cost: 20000
    

    Bridge Identifier: 32768 / 0 / 00:01:02:03:04:01
    

    Bridge Priority: 32768
    

    Bridge System ID Extension: 0
    

    Bridge System ID: 00:02:02:03:04:01
    

    

    3.