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SD-ACCESS underlay construction

Hello everyone,,

I can't seem to find decent information regarding this.

DNAC can provision the underlay network, but i find no details on how it does so.

Suppose i have a 3-level campus network: Access, Distribution, Core and Border nodes.
The underlay deployed is a routed access network.


1) By default, DNAC deploys an IS-IS underlay. Is this IS-IS underlay a single area network ?
I find it funny that Cisco itself recommends multi-area networks in the Routed Access design guides (with distributions in seperate OSPF areas, to limit LSA propagation), but then would deploy a full 3-level underlay network as a single area ??
2) With no summarization at Distribution level, only at Border Level ?

3) When DNAC provisions the underlay, what exactly is it expecting regarding connectivity ?

          * is it expecting that the distribution switches are interconnected ?

          * is it expecting that the core switches are interconnected ?

          * or both ?
           * Are these obligations or not ? Must they be interconnected or -may- they be interconnected ?

4) Up to what size is supported ? 3 distribution pairs ? 10 distribution pairs ? 50 distribution pairs. There must be some limit ? I am only talking about the underlay. I am not (yet) looking at the overlay enduser limits.

Pavan Siripuram
Cisco Employee

As per my knowledge we use only one Area , but the thing to note here is the underlay is only needed for the L3 Connectivity and it doesn't have any user routes , the only routes this underlay would be having the interconnectivity routes and if you have some DHCP , DNS and other services would be routed to them , so the number of routes will be minimal and computation will be lower , i would recommend you to go through the SDA Design guides and if you would like to get some design review please involve your Accounts team they can get right people to review your design.