I don't think you can put a single port on two VLANS unless you configured
trunking if my memory serves me right.
with Per VLAN spanning tree a particular switch can belong to multiple
instances of spanning tree and in each spanning tree instance, it might be
acting as a root bridge, some ports might be in blocking mode or forwarding
depending on what VLAN it belongs, too.
I believe the design that you had drawn shows the access layer switches are
trunking to Switch A and B to provide redundancy in case of failure in
switch A or B. Also, each switch in the access layer can run up to 2
instances of spanning tree on each VLAN which are carried through the trunk
ports only if Cisco switches are used.
Link:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/config/s
pantree.htm#xtocid2879614
Priscilla Oppenheimer <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
>
> >----- Original Message -----
> >From: AndyD <[EMAIL PROTECTED]>
> >Newsgroups: groupstudy.cisco
> >To: <[EMAIL PROTECTED]>
> >Sent: Sunday, February 18, 2001 8:58 AM
> >Subject: Equal cost switching
> >
> > > Spanning tree is supposed to choose the one best switched path. But
if
> >you
> > > set up two equal cost paths, will it use both?
>
> No, I don't think so.
>
> > Is there a way to force it
> > > to use the bandwidth from both paths?
>
> Cisco lets you implement one spanning-tree per VLAN. So with redundant
> links and VLANs, you can accomplish what you want. I can't remember
exactly
> how it works, but I think you put every port in two VLANs. I talked about
> this in my book, Top-Down Network Design, and you can see the figure for
> the design here:
>
> http://www.priscilla.com/topdownupdates.html
>
> Hope this helps a bit. Maybe somebody else remembers more details. (I
> didn't get into the details in my book, and now I've forgotten them! &;-)
>
> Priscilla
>
> > >
> > > Thanks!
> > >
>
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
>
> _________________________________
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