Why Bridge configuration filters RSTP (BPDU packets) from LAN

Discussion in 'Cisco' started by Tee Mat, Apr 2, 2006.

  1. Tee Mat

    Tee Mat Guest

    Hi,

    Any ideas why Rapid Spanning Tree protocol (802.1w) does not go through my
    cisco 827 router with bridging configuration? Every other traffic flows ok
    from LAN to WAN.

    My configuration is:
    http://www.cisco.com/en/US/products/hw/routers/ps380/products_qanda_item09186a00800949ec.shtml#q1

    http://www.cisco.com/en/US/products...on_guide_chapter09186a0080118d24.html#1015100

    With above configurations, Rapid Spanning Tree enabled switch that is
    connected to Cisco827 routers LAN, cannot sent its BPDU packets to the WAN.
    These RSTP packets seems to be blocked somehow by router? but why.. because
    every other traffic is passed.

    All i need, is pure bridge (Layer2) to the WAN.

    [switch] ---eth[Cisco827 ]atm--->ATMnet

    Is there some other configuratios to solve this, or is there some commands
    to be added this particular configuration?


    thanks,


    -T

    Tee Mat, Apr 2, 2006
    #1
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  2. Tee Mat

    Merv Guest

    Merv, Apr 2, 2006
    #2
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  3. Tee Mat

    Tee Mat Guest

    Re: Why Bridge configuration filters RSTP (BPDU packets)

    So, there is no way to say cisco827/837 routers "Take no action" to these
    RSTP packets from LAN to WAN and from WAN to LAN? I fullfil my scenario if
    there is still some solution hanging on the air.. other than using old STP
    802.1D. Thanks Merv for the first answer.

    With RFC1483 bridging configuration on both cisco827_1 and cisco827_2,
    switch_2 can now see all the traffic from switch_1 and otherwise, EXCEPT
    Rapid Spanning Tree Protocol traffic. It is blocked by routers.

    Routers should not take any actions to these RSTP packets change between
    switch_1 and switch_2. It is necessery that bridge from endpoint 1 to
    endpoint 2 is pure L2 bridge without filtering/dropping anything. There is
    no need routers to change Spanning Tree information to anywhere. Only
    switch_1 and switch_2 need to change each others spanning tree information
    through the bridge.


    LAN WAN

    endpoint 1
    -[switch_1]---[cisco827_1]---ATM
    |
    |
    -[switch_2]---[cisco827_2]---ATM
    endpoint 2


    If Cisco827/837 is not capable of doing this, any ideas which routers can
    handle this (allow RSTP flow between endpoints) ?

    Thanks,
    -T




    "Merv" <> wrote in message
    news:...
    > the router only understand 802.1D BPDU and drops RSPT BPDUs.
    >
    > The ether switch should sense the 802.1D BPDU's from the router and
    > change into compatibility mode
    >
    > see
    >
    > http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#comp802
    >
    Tee Mat, Apr 2, 2006
    #3
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