Well actually, if you really mean hub and spoke, you will NOT have 99 PVCs per
site. Or two per site in the original example. You'll have 99 PVCs
connecting to the hub site, and one at each spoke site.
You seem to be confusing hub and spoke with full mesh, where every site is
directly connected to every other site. For N sites, a full mesh network will
indeed have N-1 PVCs attached to each site (a total of (N-1)*N/2 in the whole
network). Generally, full mesh networks are regarded as being, shall we say, a
bit over the top for anything other than very small numbers of sites.
A hub and spoke design has a single hub site and multiple spoke sites, with a
single PVC from the hub to each spoke, and no PVCs directly between the spoke
sites. If there's N sites (including the hub), then there's a total of N-1 PVCs
in the whole network. Other options are partial mesh (take a full mesh and
remove links that don't get significant traffic, thus reducing the number of
links and therefore cost and management effort), or distributed hub and spoke
(not sure if that's the correct term but it describes it well - main hub has
PVCs to secondary hubs, which have PVCs to spoke sites). Or combinations of the
above.
If you're doing a hub and spoke design, you can get around the single point of
failure issue by having a multi-homed hub and spoke design - have two hubs and
each spoke has PVCs to each hub. Doubles the number of PVCs, but some carriers
offer 'backup PVCs' at a lower cost - they only kick in if the main PVC fails.
Or you can back up your frame network with ISDN or some other on-demand service.
JMcL
---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 16/06/2000 08:56
---------------------------
Phil Barker <[EMAIL PROTECTED]> on 16/06/2000 00:03:07
Please respond to Phil Barker <[EMAIL PROTECTED]>
To: cisco cabanaboy <[EMAIL PROTECTED]>
[EMAIL PROTECTED]
cc: (bcc: JENNY MCLEOD/NSO/CSDA)
Subject: Re: frame-relay design
Assuming one Hub and 99 spokes you would need 99
"frame-relay interface-dlci" statements per site if
you wanted to talk to every remote site.
I cannot see this being a practicle solution
though, i.e You would be committing a massive 'single
point of failure at the Hub', plus I very much doubt
that all the sites would want direct access to each
other anyway.
HTH
Phil.
--- cisco cabanaboy <[EMAIL PROTECTED]> wrote:
> If you had 3 locations in a hub and spoke topology,
> then you would want two pvcs going to each
> site...(using subinterfaces), how do the numbers
> change as you add remote sites...
>
> e.g. if you add the 4th site, do you have to add a
> pvc
> to every other site?, totalling 3 pvcs/subinterfaces
> ?
>
> so would that mean if you had 100 sites it would
> require n-1 (99) pvcs/dlcis/subints per location...?
>
>
> i may be way off
>
> -thanks
>
>
>
>
> =====
> ciscocabanaboy, CCNP-Voice, CCDP, MCSE, CNX, A+, N+,
> I-net+, BOFH...
>
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