tl/dr: RFC1918 (private) addresses are categorized as E/W by VRNI by default, non-RFC1918 (public) addresses are categorized as N/S by default. You can flag private as N/S or public as E/W to ensure the reports reflect your environment.
Looking over the vRNI docs I ran into an interesting description. Note these statements
There seems to be confusion and contradictions there. I would rewrite this as:
Defined by the IETF as private IP addresses, RFC1918 sets aside the networks 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 for private or non-Internet use.
VRNI classifies any IP address range addressed by the RFC1918 standard as East-West, which is traffic that is “internal” to your data center. If you have addresses or networks outside of the RFC1918 range you would like classified as East/West, you can add those IPs to the East/West range. This can be used for stretched clusters, hybrid clouds or any scenario where part of your data center is accessed by a public IP address.
VRNI classifies any IP addresses not covered by the RFC1918 standard as North-South, which is traffic to or from a source “outside” of your data center. If you have addresses or networks in the private address space you would like classified as North/South you can add those networks to the North/South range. This is useful for environments were you have remote users or remote data centers accessed by private IP ranges but you want the traffic classified as North/South in your VRNI reports.