Rapid STP in the WAN?

Discussion in 'Cisco' started by wayne, Aug 9, 2007.

  1. wayne

    wayne Guest

    Scenario...

    11 switches in a loop. Total distance of the loop is 200 miles (not
    sure that the distance matters...). Point to point connections between
    switches.

    1
    / \
    / \
    / \
    11 2
    / \
    / \
    / \
    10 3
    / \
    / \
    / \
    9 4
    \ /
    \ /
    \ /
    8 5
    \ /
    \ /
    \ /
    7---X---6

    1 is root, break in the loop occurs between 6 and 7.

    Side question: reading RSTP documents, it appears the recommended number
    of bridges in an STP instance is 7. Is this 7 from the ROOT or 7
    END-TO-END?

    Anyway, Now suppose a few "spurs" are introduced into the topology,
    connected to switches 6 and 7...spur 1 and spur 2 are effectively 13
    hops from each other and 230 miles or so.

    1
    / \
    / \
    / \
    11 2
    / \
    / \
    / \
    10 3
    / \
    / \
    / \
    9 4
    \ /
    \ /
    \ /
    8 5
    \ /
    \ /
    \ /
    7---X---6
    / \
    / \
    spur1 spur2


    I'm not a great spanning-tree mind, but this seems like a disaster
    waiting to happen.

    Am I wrong? Are there ways to tune RSTP to make this dream a reality?
     
    wayne, Aug 9, 2007
    #1
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  2. wayne

    Merv Guest

    Are there ways to tune RSTP to make this dream a reality?

    yes disable it

    STP/RSTP is a distributed virus
     
    Merv, Aug 9, 2007
    #2
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  3. wayne

    wayne Guest

    Merv wrote:
    > Are there ways to tune RSTP to make this dream a reality?
    >
    > yes disable it
    >
    > STP/RSTP is a distributed virus
    >
    >



    You are preaching to the choir.

    However, this has been presented as an option by a VAR and management is
    seriously considering it since it's the LOWEST BID! It's a MetroE/QinQ
    solution with ME3400 switches.

    ug.

    I'm recommending a different bid that is a routed VRF-lite network using
    3560E switches (there are multiple networks that need isolation yet run
    over the same physical infrastructure).

    There is one VLAN that needs to be dropped at multiple locations, that
    one can be tunneled, or we can just deal with RSTP on the one VLAN, it's
    not that important anyway.
     
    wayne, Aug 9, 2007
    #3
  4. wayne

    Merv Guest

    YeahI can just see what is going to start happening with Metro
    Ethernet - companies will start building flat networks again just like
    they did when VLAN switches appeared...

    And then the mop-up operation starts all over again ...
     
    Merv, Aug 9, 2007
    #4
  5. wayne

    stephen Guest

    "wayne" <> wrote in message
    news:eTKui.1356$...
    > Merv wrote:
    > > Are there ways to tune RSTP to make this dream a reality?
    > >
    > > yes disable it
    > >
    > > STP/RSTP is a distributed virus
    > >
    > >

    >
    >
    > You are preaching to the choir.
    >
    > However, this has been presented as an option by a VAR and management is
    > seriously considering it since it's the LOWEST BID! It's a MetroE/QinQ
    > solution with ME3400 switches.


    3400s understand IP routing....
    http://www.cisco.com/en/US/products/ps6580/tsd_products_support_series_home.html

    look in the config guide. reads like a 3560 but without VRFs.
    >
    > ug.
    >
    > I'm recommending a different bid that is a routed VRF-lite network using
    > 3560E switches (there are multiple networks that need isolation yet run
    > over the same physical infrastructure).


    if you have L3 devices at each site, ask for dual interfaces, or separate
    pt - pt VLANs, and do the topology bit yourself?
    >
    > There is one VLAN that needs to be dropped at multiple locations, that
    > one can be tunneled, or we can just deal with RSTP on the one VLAN, it's
    > not that important anyway.


    a spanning tree storm will melt either complete links, or the entire set of
    switches - so you probably do care.....

    --
    Regards

    - replace xyz with ntl
     
    stephen, Aug 10, 2007
    #5
  6. wayne

    wayne Guest

    stephen wrote:
    > "wayne" <> wrote in message
    > news:eTKui.1356$...
    >> Merv wrote:
    >>> Are there ways to tune RSTP to make this dream a reality?
    >>>
    >>> yes disable it
    >>>
    >>> STP/RSTP is a distributed virus
    >>>
    >>>

    >>
    >> You are preaching to the choir.
    >>
    >> However, this has been presented as an option by a VAR and management is
    >> seriously considering it since it's the LOWEST BID! It's a MetroE/QinQ
    >> solution with ME3400 switches.

    >
    > 3400s understand IP routing....
    > http://www.cisco.com/en/US/products/ps6580/tsd_products_support_series_home.html
    >
    > look in the config guide. reads like a 3560 but without VRFs.


    Depends on the image. METROIPACCESS yes, METROACCESS and METROBASE, no.
    The proposal had METROACCESS in the WAN, with L3 devices connected to
    QinQ ports on the WAN switches.

    > a spanning tree storm will melt either complete links, or the entire set of
    > switches - so you probably do care.....
    >


    You are right, good point.

    For what it's worth, I talked to my immediate supervisor and explained
    my concerns with the low bid, he agreed and will bring it up with the
    Deciders.
     
    wayne, Aug 11, 2007
    #6
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