switches, spanning tree question regarding designated ports and switches

Discussion in 'Cisco' started by alefveld@versatel.nl, Dec 18, 2008.

  1. Guest

    Hi,
    As far as i understand STP, every switch has one RP with the lowest
    path cost back to the root switch. If a segment exists with multiple
    switches attached to it, as in the case of redundancy, am i correct in
    assuming:

    1. there is only 1 switch which is designated switch and has 1
    designated port upon which it forwards frames as it is explained in
    the books
    2. what does the other switch do ? block everything ?

    I think 1 switch allows everything and the other switch blocks
    everything except for 1 Designated port which it uses for what exactly
    ?

    I'm a bit lost here, i understand until the RP concept, after that i'm
    slightly confused.

    Can anyone put me back on track here?
    Much appreciated. Also a link to STP loops explained would be welcome,
    i only see documents with bridge loops explained, but as these are
    transparent, i think they work slighly different then a modern switch?

    Kind regards,
    bm
     
    , Dec 18, 2008
    #1
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  2. donjohnston

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    1) Another way (the way I prefer) of expressing it is: On any segment, there is only one designated port. All other ports are either root or non-designated (blocking)

    2) See #1 :)

    The thing with bridges and switches is that they're basically the same. That's why we use term like "root bridge" and "bridge ID"
     
    donjohnston, Dec 30, 2008
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