[c-nsp] Limits of STP/RSTP/REP?

[Ross Vandegrift]

On Thu, May 21, 2009 at 04:54:40PM +0300, Tassos Chatzithomaoglou wrote:
> switch(config)#spanning-tree vlan 7 root primary ?
>   diameter  Network diameter of this spanning tree
>   <cr>
> 
> switch(config)#spanning-tree vlan 7 root primary diameter ?
>   <2-7>  Maximum number of bridges between any two end nodes

Are those are numbers for classic PVST?  RST allow for larger diameter
networks because TCNs don't have to propogate to the root and then
back down.  My numbers come from the MST version:

lab(config)#spanning-tree mst max-hops ?
  <1-255>  maximum number of hops a BPDU is valid

Ross

> 
> 
> --
> Tassos
> 
> Tassos Chatzithomaoglou wrote on 21/05/2009 16:43:
> >I had the impression that STP diameter defined the max number of bridges 
> >between 2 points.
> >And the recommended value by the IEEE was 7 (using default timers).
> >
> >-- 
> >Tassos
> >
> >?????? ???????? wrote on 21/05/2009 12:25:
> >>>Definitely not more than 20 in a ring.  As far as I know, IOS limits
> >>>the value of max-hops to 20.  This means you can't have a BPDU
> >>>traverse more than 20 hops without being thrown away.  If one pair of
> >>>switches in the ring experienced a total cut, your network would have
> >>>a diameter of 20, end to end.
> >>
> >>this is STP limitation: MaxAge is by default 20 hops.
> >>for IOS, you can change this value:
> >>
> >>Switch(config)#spanning-tree vlan 1 max-age ?
> >>  <6-40>  maximum number of seconds the information in a BPDU is valid
> >>or for MST
> >>Switch(config)#spanning-tree mst max-age ?
> >>  <6-40>  maximum number of seconds the information in a BPDU is valid
> >>
> >>value 40 is maximum bpdu hopcount for 3560 switch, for other models
> >>there can be other upper limit.
> >>
> >>-- 
> >>wbr
> >>sergey khalavchuk
> >>_______________________________________________
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> >
> >
> 
> -- 
> ****************************
>   Tassos Chatzithomaoglou
>  Backbone & Access Networks
>        FORTHnet S.A.
>     <achatz at forthnet.gr>
> ****************************
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-- 
Ross Vandegrift
ross at kallisti.us

"If the fight gets hot, the songs get hotter.  If the going gets tough,
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