Rapid PVST+: All switches at FWD state

Hi there,

I would like to know if it is possible to have all three switches' ports at FWD state although Root Bridge has been configured properly. The following is configuraiton I used to configure the switches. Please also refer the attached photos of my "show spanning-tree vlan 200".

Configuration
SW1 - Root Primary Bridge
spanning-tree vlan 200 root primary

SW2 - Root Secondary Bridge
spanning-tree vlan 200 root secondary

Any explanation or discussion would be greatly appreciated. Thanks in advance.



Comments

  • I'm new to CCNA, so I'm learning from this post as well. But, I'm seeing Routers as part of your topology on all switches. So you're not giving us the fool topology here. Or, is that happening because these are multi layer switches?
    One thing I learned is there is either a mistake somewhere or you're not giving us full info. If something doesn't make sense it's because you missed something.

  • L2 protocols may have weird behabiours on virtualized technilogies as Keith underlined in one of his CCNA lessons.

    I've created the same topology in my virtual enviornment with EVE-NG and all seems fine:

    note: you put root secondary on SW3.

    Here the SW1
    SW1#show spann vlan 200

    VLAN0200
      Spanning tree enabled protocol rstp
      Root ID    Priority    24776
                 Address     aabb.cc00.6000
                 This bridge is the root
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
    
      Bridge ID  Priority    24776  (priority 24576 sys-id-ext 200)
                 Address     aabb.cc00.6000
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time  300 sec
    
    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0               Desg FWD 100       128.1    Shr Peer(STP) 
    Et0/1               Desg FWD 100       128.2    Shr 
    
    
    SW1#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                      S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                      D - Remote, C - CVTA, M - Two-port Mac Relay 
    
    Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
    SW2              Eth 0/1           138             R S I  Linux Uni Eth 0/0
    SW3              Eth 0/0           135             R S I  Linux Uni Eth 0/1
    
    Total cdp entries displayed : 2
    

    SW2:

    SW2#show spann vlan 200
    
    VLAN0200
      Spanning tree enabled protocol rstp
      Root ID    Priority    24776
                 Address     aabb.cc00.6000
                 Cost        100
                 Port        1 (Ethernet0/0)
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
    
      Bridge ID  Priority    32968  (priority 32768 sys-id-ext 200)
                 Address     aabb.cc00.7000
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time  300 sec
    
    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0               Root FWD 100       128.1    Shr 
    Et0/1               Altn BLK 100       128.2    Shr Peer(STP) 
    
    
    SW2#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                      S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                      D - Remote, C - CVTA, M - Two-port Mac Relay 
    
    Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
    SW1              Eth 0/0           178             R S I  Linux Uni Eth 0/1
    SW3              Eth 0/1           178             R S I  Linux Uni Eth 0/0
    
    Total cdp entries displayed : 2
    

    and, SW3:

    SW3#show spann vlan 200
    
    VLAN0200
      Spanning tree enabled protocol ieee
      Root ID    Priority    24776
                 Address     aabb.cc00.6000
                 Cost        100
                 Port        2 (Ethernet0/1)
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
    
      Bridge ID  Priority    28872  (priority 28672 sys-id-ext 200)
                 Address     aabb.cc00.8000
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time  15  sec
    
    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0               Desg FWD 100       128.1    Shr 
    Et0/1               Root FWD 100       128.2    Shr 
    
    
    SW3#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                      S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                      D - Remote, C - CVTA, M - Two-port Mac Relay 
    
    Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
    SW1              Eth 0/1           128             R S I  Linux Uni Eth 0/0
    SW2              Eth 0/0           169             R S I  Linux Uni Eth 0/1
    
    Total cdp entries displayed : 2
    

    I hope this helps.

  • Looks to me from your graphic that you're using Cisco's Packet Tracer tool. I also encountered the same thing when working up a Spanning-Tree lab in Packet Tracer. I'm pretty sure it's a bug in the software. To fix it, I saved my config and then reloaded all three switches. Once they came back up all was fine.

  • @kbogart said:
    Looks to me from your graphic that you're using Cisco's Packet Tracer tool. I also encountered the same thing when working up a Spanning-Tree lab in Packet Tracer. I'm pretty sure it's a bug in the software. To fix it, I saved my config and then reloaded all three switches. Once they came back up all was fine.

    Hi Keith,

    Thanks for your suggestion. I am using GNS3 with Cisco vIOS L2 image for switch as EtherChannel Switch has very limited features for switching lab. Second time I tried the same lab from scratch in GNS3, I had no issue. Maybe I missed something in config or GNS3 is buggy for vIOS L2 image.

    Since I learnt your GNS3 free course on INE, I never went back to Packet Tracer. Thanks a lot for your enlightment, Keith.

  • @Profchaos911 said:
    I'm new to CCNA, so I'm learning from this post as well. But, I'm seeing Routers as part of your topology on all switches. So you're not giving us the fool topology here. Or, is that happening because these are multi layer switches?
    One thing I learned is there is either a mistake somewhere or you're not giving us full info. If something doesn't make sense it's because you missed something.

    Hey Profchaos911,

    Yes. All those switches are L3 switches. L3 switches would act exactly the same as L2. As I am using GNS3 for all of my lab works, what I have found out is GNS3 is buggy sometimes. So sorry if I confused in any possible way. Thanks for your comments.

  • @kbogart said:
    Looks to me from your graphic that you're using Cisco's Packet Tracer tool. I also encountered the same thing when working up a Spanning-Tree lab in Packet Tracer. I'm pretty sure it's a bug in the software. To fix it, I saved my config and then reloaded all three switches. Once they came back up all was fine.

    Hi Keith,

    I have been using GNS3 since I learnt GNS3 free course on INE. I used Cisco vIOS L2 image with GNS3 for the lab. Second time I tried the same lab from scratch, it was fine on GNS3. Maybe GNS3 was buggy. Thanks for your insight though.

  • @harpreet_singh said:
    L2 protocols may have weird behabiours on virtualized technilogies as Keith underlined in one of his CCNA lessons.

    I've created the same topology in my virtual enviornment with EVE-NG and all seems fine:

    note: you put root secondary on SW3.

    Here the SW1
    SW1#show spann vlan 200

    VLAN0200
    Spanning tree enabled protocol rstp
    Root ID Priority 24776
    Address aabb.cc00.6000
    This bridge is the root
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

    Bridge ID Priority 24776 (priority 24576 sys-id-ext 200)
    Address aabb.cc00.6000
    Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
    Aging Time 300 sec

    Interface Role Sts Cost Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0 Desg FWD 100 128.1 Shr Peer(STP)
    Et0/1 Desg FWD 100 128.2 Shr


    SW1#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
    S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
    D - Remote, C - CVTA, M - Two-port Mac Relay

    Device ID Local Intrfce Holdtme Capability Platform Port ID
    SW2 Eth 0/1 138 R S I Linux Uni Eth 0/0
    SW3 Eth 0/0 135 R S I Linux Uni Eth 0/1

    Total cdp entries displayed : 2

    SW2:

    SW2#show spann vlan 200
    
    VLAN0200
      Spanning tree enabled protocol rstp
      Root ID    Priority    24776
                 Address     aabb.cc00.6000
                 Cost        100
                 Port        1 (Ethernet0/0)
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
    
      Bridge ID  Priority    32968  (priority 32768 sys-id-ext 200)
                 Address     aabb.cc00.7000
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time  300 sec
    
    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0               Root FWD 100       128.1    Shr 
    Et0/1               Altn BLK 100       128.2    Shr Peer(STP) 
    
    
    SW2#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                      S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                      D - Remote, C - CVTA, M - Two-port Mac Relay 
    
    Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
    SW1              Eth 0/0           178             R S I  Linux Uni Eth 0/1
    SW3              Eth 0/1           178             R S I  Linux Uni Eth 0/0
    
    Total cdp entries displayed : 2
    

    and, SW3:

    SW3#show spann vlan 200
    
    VLAN0200
      Spanning tree enabled protocol ieee
      Root ID    Priority    24776
                 Address     aabb.cc00.6000
                 Cost        100
                 Port        2 (Ethernet0/1)
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
    
      Bridge ID  Priority    28872  (priority 28672 sys-id-ext 200)
                 Address     aabb.cc00.8000
                 Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
                 Aging Time  15  sec
    
    Interface           Role Sts Cost      Prio.Nbr Type
    ------------------- ---- --- --------- -------- --------------------------------
    Et0/0               Desg FWD 100       128.1    Shr 
    Et0/1               Root FWD 100       128.2    Shr 
    
    
    SW3#show cdp neigh
    Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                      S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone, 
                      D - Remote, C - CVTA, M - Two-port Mac Relay 
    
    Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
    SW1              Eth 0/1           128             R S I  Linux Uni Eth 0/0
    SW2              Eth 0/0           169             R S I  Linux Uni Eth 0/1
    
    Total cdp entries displayed : 2
    

    I hope this helps.

    Hi harpreet_singh,

    Thanks for your effort to test it out. Much appreciated.

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