[c-nsp] daisy-chain hop limit

[Paul Wozney]

On Mon, Mar 14, 2011 at 03:31, Nick Hilliard <nick at foobar.org> wrote:

> On 14/03/2011 09:46, Marco Regini wrote:
>
>> i have to daisy-chain 28 cisco switch, my humble is only about
>> spanning-tree (rapid-pvst).
>>
>
> Here's what happened one hospital which did something like what you're
> planning to do:
> http://www.cio.com.au/article/65115/all_systems_down/


Scalability?  none.
Performance?  poor.
Stability?  questionable.

Additional cabling isn't terribly expensive, and it is a capital expense at
that so once it is in you can recoup the benefits for years to come.  Get a
core switch to aggregate your 28 access switches - if your cabling
infrastructure is copper this is pretty easy, and if your runs are greater
than 100m then I'm sure someone on the list could recommend a good fiber
aggregation switch.

The story Nick linked is a good one to illustrate the potential pain of
exceeding the recommended STP diameter, and you should also read the SRND on
campus network design.  I know it looks like it is written for large
enterprise organizations, but the same approach works in the SMB designs.
http://www.cisco.com/en/US/solutions/ns340/ns414/ns742/ns815/landing_cOverall_design.html

---
Paul Wozney
Network Consultant
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