Should we accept VNI zero?

[daniel-noland]

I can't find anything in the official VXLAN spec (RFC7348) which precludes zero as a valid VNI.

It looks like the Linux kernel and OVS both accept 0 as a valid VNI, while Arista documentation states

VNI values range from 1 to 16777215

--- EOS 4.33.1F User Manual

Aruba also takes this stance

Range: 1 to 16777214.

--- Aruba Help Center - VNI

In a capricious deviation from the RFC, Cisco documentation states that

It is typically a 24-bit value part of the VXLAN header, which can support up to 16 million individual network segments. (Valid VNI values are from 4096 to 16,777,215.)

--- Implementing Data Center Overlay Protocols

We need to decide what we want to do here in terms of validity checks.