Multisite EVPN with Cisco BGWs

Hello,

I'm working on EVPN Multisite solution based on Cisco Nexus 9k switches. Currently I have prepared one site with eBGP as under and overlay routing - 2x Spine in one AS and 2x vPC pair leaf switches in separated AS.

This solution works fine for L2 EVPN and is full compliant with RFC - works with pair of Cumulus switches in clag as extra leaves.

In next step I want to prepare mirrored site and connect them together by 2x BGWs and 1x SuperSpine layers/ per site.

If found some documentation: https://www.cisco.com/c/en/us/products/collateral/switches/nexus-9000-series-switches/white-paper-c11-739942.html

But in most important part they send me to "For more information" chapter without giving any answer :(

Questions:

• BGWs should be in different AS then SuperSpine and Spine switches?

• BGWs should have full VNI base - sum of all VNI in same site/both sites?

• Is iBGP session between BGWs necessary?

• Do you seen any whitepapers or working deploymend?

Sorry for my english - is not my native language. And of course thanks for answers.