StackWise Virtual in SD-Access and Layer 3 Routed Access Networks

[g.pregnolato]

I am designing a campus LAN infrastructure based on Cisco SD-Access solution.

My end-customer campus consists of 6 buildings. In the current network, there is a couple of distribution switches in each building connected, with two fiber-optic links, to the core switches in the main building.

The Software-Defined Access Solution Design Guide (June 2020) states that "In a Layer 3 routed access environment, two separate, physical switches are best used in all situations except those that may require Layer 2 redundancy."

If I use two separate switches as distribution/intermediate nodes I need four fiber-optic links, instead of the current two, to connect to the two core (Border + Control Plan nodes) switches. If, on the other hand, I used the two distribution/intermediate nodes, configured in a StackWise Virtual manner, a couple of fiber optic links could suffice to connect to the core switches.

If I were forced to use the StackWise Virtual on the intermediate nodes, the design would not be supported? What would be the contraindications on the performance of the SD-Access fabric?

[balaji.bandi]

You can use same 2 Fibre network going to different uplink side, since this is Routed Environment, if one of the route/device/fibre  fail, other route can take over ? in ECMP right ?

Hope the Core Switch also running Router mode right ?in SD-Access fabric.

other thing note : if the Intermediate Node located in different comms room, then your point still valid. SVL defeat the purpose of SD-Access i guess here.

[g.pregnolato]

As per Software-Defined Access Solution Design Guide "Core switch peer devices should be cross linked to each other. Distribution switches within the same distribution block should be crosslinked to each other and connected to each core switch." If I configure the two switches of the same distribution block as two separate entities (no SVL) I'll build a squared topology that is not recommended. 

So my doubt remains: with two only fiber links from each distribution block to the core switches (no SVL) is it better to configure the two distribution switches as a single virtual switch (SVL) or as two separate switches (no SVL)?

What would be the contraindications on the performance of the SD-Access fabric if I used SVL switches on each distribution block?