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

  • MartinlMartinl ✭✭✭

    weird indeed, 1 port on link sw2 =sw3 should be blocking,
    check trunks, make sure all links are trunking and check allowed vlans

  • 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.

  • MartinlMartinl ✭✭✭

    most common mistake or miss-config is not trunking between switches

  • 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.

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