PVST+ and RSTP

Hi Guys,

Can you please tell me what is the difference between PVST+ and RSTP.

Is PVST+ a proprietary implementation of RSTP by Cisco?


Core#sh spanning-tree

VLAN0001
  Spanning tree enabled protocol rstp

This is output from a Cisco switch. I expected to seee protocol pvst+ here. But it shows as rstp.

Comments

  • Hi Krishnar,

    PVST+ is the proprietary cisco protocol with some enhancement to 802.1D whish is a common spanning tree protocol. When you are running PVST+ you will see the out put like " Spanning tree enabled protocol ieee ".

    RSTP is 802.1w which is the IEEE standard protocol and it is use with 802.1s which is MST.

    Cisco proproetary implementation of RSTP (802.1w) is rapid-pvst+.

    IEEE standard 802.1w is used by 802.1s which is MST/MSTP

    when we use rapid-pvst+ the output of cisco switches shows rstp as a output

    HTH

     

  • Ok.. That means that the above mentioned switch is using rapid-pvst+.

  • Yes, PVST+ is the default mode for the C3560s. You can simply change it using "spanning-tree mode" command.

  • yes exactly

    .ili.ili.


    Mahir Ali Ahmed
    Senior Specialist Service & Infrastructure Operations
    The past is dead ! The future, yet unborn ! Time to live in the present. Time to move on !



    On Mon, Nov 4, 2013 at 11:25 PM, krishnar <[email protected]> wrote:

    Ok.. That means that the above mentioned switch is using rapid-pvst+.




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  • I was under the impression that if we see STP type as ieee, then its is PVST+ which is not rapid STP.

    But when I check here I see the type as ieee.



    image

     

    And the blocked port port in Alternate state which is only in RSTP. I was thinking that this should have been shown as BLK as there is not Alternate port in 802.1D.

    Can anyone please help?

     

  • I was thinking that if the STP type is shown as ieee, then its PVST+ which is not Rapid.

    image

    But when I check there I see the type as ieee and port role is shown as Alternate which is a RSTP port role.

    Am I wrong in my understanding?

  • I was thinking that if we see the STP type as ieee, then its PVST+ which is not a rapid one.

    But here I see type as ieee and the port role as Alternate which is TSTP port role.

    Cat2#show spanning-tree vlan 1

    VLAN0001
      Spanning tree enabled protocol ieee
      Root ID    Priority    24577
                 Address     0018.1820.2700
                 Cost        19
                 Port        23 (FastEthernet0/23)
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

      Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
                 Address     000b.46e2.6980
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time 300

    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Fa0/23              Root FWD 19        128.23   P2p
    Fa0/24              Altn BLK 19        128.24   P2p

    Am I wrong in my understanding?

  • Hi Krishna,

    I think you are running rapid-pvst mode in your switch. Please check the mode using "show spanning-tree summary" command.

    Here is the example:

    Rack1Sw2#sh spanning-tree summary

    Switch is in rapid-pvst mode

    Root bridge for: none

    Extended system ID           is enabled

    Portfast Default             is disabled

    PortFast BPDU Guard Default  is disabled

    Portfast BPDU Filter Default is disabled

    Loopguard Default            is disabled

    EtherChannel misconfig guard is enabled

    UplinkFast                   is disabled

    BackboneFast                 is disabled

    Configured Pathcost method used is short

     

    Good luck!

  • Hi Krishnar,

    Can you check the output of your switch

    ====
    Rack1SW1#sh span summary
    Switch is in pvst mode
    Root bridge for: none
    Extended system ID           is enabled


    Portfast Default             is disabled
    PortFast BPDU Guard Default  is disabled
    Portfast BPDU Filter Default is disabled
    Loopguard Default            is disabled
    EtherChannel misconfig guard is enabled
    UplinkFast                   is disabled


    BackboneFast                 is disabled
    Configured Pathcost method used is short
    ===
    Rack1SW1#sh span sum
    Switch is in rapid-pvst mode
    Root bridge for: none
    Extended system ID           is enabled


    Portfast Default             is disabled
    PortFast BPDU Guard Default  is disabled
    Portfast BPDU Filter Default is disabled
    Loopguard Default            is disabled
    EtherChannel misconfig guard is enabled
    UplinkFast                   is disabled


    BackboneFast                 is disabled
    Configured Pathcost method used is short
    ====

    .ili.ili.


    Mahir Ali Ahmed
    Senior Specialist Service & Infrastructure Operations
    The past is dead ! The future, yet unborn ! Time to live in the present. Time to move on !



    On Wed, Nov 6, 2013 at 10:39 PM, krishnar <[email protected]> wrote:

    I was thinking that if we see the STP type as ieee, then its PVST+ which is not a rapid one.

    But here I see type as ieee and the port role as Alternate which is TSTP port role.

    Cat2#show spanning-tree vlan 1



    VLAN0001
      Spanning tree enabled protocol ieee
      Root ID    Priority    24577
                 Address     0018.1820.2700
                 Cost        19
                 Port        23 (FastEthernet0/23)


                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

      Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
                 Address     000b.46e2.6980
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec


                 Aging Time 300

    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Fa0/23              Root FWD 19        128.23   P2p


    Fa0/24              Altn BLK 19        128.24   P2p

    Am I wrong in my understanding?




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  • Okay

    Cisco Rapid-pvst syntax = Rapid PVST+

    Cisco pvst syntax = PVST+

    But what if lab exam ask you to enable 802.1w ?

    Does that mean now Rapid PVST+ becomes orignial Rapid PVST spec ? [;)]

    Funny Cisco [:P]

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