This read-only integer, part of the VXLAN tunnel statistics table's index alongside the peer and source IP addresses, identifies the VNI (VXLAN Network Identifier) whose tunnel counters a row reports; the MIB's own DESCRIPTION text for this field oddly reads "VRF index," but the object's name and table position clearly correspond to a VNI number, not a VRF. Admins use it, together with the peer and source IP, to pinpoint exactly which VXLAN segment's traffic counters (packets and bytes received and transmitted) a particular statistics row represents. For example, an entry with hwVxlanTunnelStatisticVni of 5000 identifies the received and transmitted counters in that row as belonging to VNI 5000's tunnel between the given source and peer addresses.