Sure you have all valid questions and my answers are based from design guide:
Please find your requested answers below:
1. In vPC VTEP scenario with MP-BGP EVPN VXLAN do we need to have the vPC peers to be BGP adjacent? if YES, why we need this adjacency?
Answer: No, we dont need vPC peers to form BGP adjaceny amongst each other
2. Can you explain why we need VRF overlay VLAN and SVI for VXLAN routing?
Answer: VRF allows to create multiple tenants which can have over-lapping address
3. Why VRF overlay SVI does NOT have an IP address assigned?
Answer: Because for VXLAN routing, the local VTEP needs to rewrite the inner destination MAC address to that of remote VTEP's router MAC Address.
4. DCI between two DCs with a pair of vPC VTEPs in each. The DCs are interconnected through a multihop MP-eBGP.
4.1 can you propose me a documentation regarding the this design?
4.2 is the full-mesh eBGP between the four VTEPs is the proper solution?
4.3 should I distribute the MP-BGP EVPN routes into inter-DC IGP?
4.4 how I must tune the MP-BGP to use both opposite VTEPs for load balancing?
Answer: VXLAN Control Plane for DCI currently can be considered as work in-progress. It was not originally meant for this solution but it has all bits-n-pieces to be used as DCI.
There is good blog post on this topic by Yves - http://yves-louis.com/DCI/?p=965 It covers scenarios and packet walks as well.
For details on specific DCI design and best-practises, i would recommend to reach out to your local Cisco Representative or Network Consulting Engineer who can help you to design DCI-VXLAN as per your network requirements.
I am currently looking for information on Vxlan as a DCI specifically DCI between two DCs with a pair of vPC VTEPs in each. Would you be able to provide me with a good design guide and possible configuration example and this type of setup.
Thanks So Much
I hope my question is not out of the scope, as it is related to Nexus switches and VXLANs: customer decided to use NSX and part of the design includes Cisco spine-and-leaf switches. However, we can't agree if we should use NX-OS (with N93936 as leafs and N9508 as spine switches) or ACI approach. Can we even provide vPC functionality if first scenario is used (one with NX-OS)?
Its very fair question to ask. Yes you can provide vPC functionality with Nexus 9000 switches using VXLAN. Below link gives more details on vPC deployment on VXLAN
Thanks for your swift response Vishal!
Here is the detail that bothers me: vPC requires two neighboring switches to be connected with peer-link but spine-and-leaf topology doesn't allow two leafs to be directly connected, right? I'm talking here about N9ks running NX-OS (not ACI) and I even found one article (link below) where spine-and-leaf topology is described but vPC is not mentioned at all. So, I'm looking for your help to clarify if vPC will work in that scenario (N9ks running NX-OS in spine-and-leaf topology)?
That is very good question - Yes Leaf-Spine Topology design doesn't allow two leafs to be connected with each other. But vPC on Leaf-Spine fabric is special design and it is supported on Nexus 9ks (standalone mode).
The guide you are referring is basic configuration on Nexus 9k platform for features like POAP, Terminal settings, File Systems and so on..
Please refer to link below on VXLAN-vPC Configuration: