[c-nsp] Leaf and Spine / CLos topology - Access Layer - why always one switch shown?

[James Bensley]

On 19 August 2016 at 16:39, Nick Cutting <ncutting at edgetg.com> wrote:
> Every single document / Diagram showing Leaf and Spine network topologies has ONE switch at the leaf layer for servers to connect to.  This goes for Cisco / Juniper / Dell
>
> I would have thought that if you had a pair of TOR switches that they would be connected at L2 and run VPC or LBT (vmware concept) down to the servers, but I cannot see this detail in any Cisco design documents.  Obviously these are connected to each spine switch upstream at L3.


Hi Nick,

One point of note is that in a DC LAN environment we get the economy
of scale somewhat, for large or hyper scale deployments there is no
need to dual home servers to dual ToR switches; we case loose a switch
(and thus a rack) or an indiviudal server without impact to service.
If $dayjob wanted to dual ToR all their racks no only would that be
hundreds and hundreds of racks that need an extra switch, all the
extra patching to each server, all the servers need an extra NIC, we
need extra spines, more patching to the spines etc. Its a significant
cost hike (nearly double) the original price.

Cheers,
James.