[c-nsp] SD-WAN design for large scale

[Brian Knight]

On 2020-03-26 05:51, adamv0025 at netconsultings.com wrote:
>> daniel.dib at reaper.nu
>> Sent: Tuesday, March 24, 2020 10:27 AM
>> 
>> Cisco SD-WAN doesn't use DMVPN, it uses OMP for control plane and 
>> IPSec
>> for data plane.
>> 
>> Omar: Yes, by default you will have a full mesh of tunnels. It's easy 
>> to build
>> Hub and Spoke topology if you want to. Often large organizations build
>> regional Hub and Spoke where you traverse a Hub to go to another
>> geographical region, such as EU to US etc.
>> 
> Is that the case really?
> When we were reviewing sd-wan solutions from a number of vendors last
> year -my recollection is that hub and spoke or dual hub and spoke (but
> not multi-hub and spoke) was their go to topology and most of them
> didn't even considered full-mesh of tunnels between spoke sites until
> I asked.

Yes.  Full mesh is the default for Cisco.  They do recommend changing 
the default if your org has more than 50 sites (I believe that number's 
right).

> If you consider what sd-wan is selling, its MPLS like QOE over cheapo
> Internet links - for which they need at least two (ideally more)
> links, then the number of tunnels is going to be n(n-1)/2 times the
> number of cheapo links to the spoke site.

Correct -- n is the number of transport links, not the number of 
devices.

> 
> 
> adam

-Brian