So far on 2 occasions we have noticed that the network zones assigned to our server nics has been changed without any interaction on our part. This is out of a few hundred servers we manage.
Case 1) Server 2008R2, 2 Network Adapters. 1 x LAN labeled in the Domain zone, and 1 x SAN in the private zone. We noticed some SAN traffic was being blocked, and lo and behold the SAN nic now showed the Domain zone.
Case 2) Server 208R2, 2 Network Adapters. 1 x LAN labeled in the Domain zone, and 1 x SAN in the Private zone. Noticed SAN traffic being blocked, discovered the SAN nic had been labeled Public.
Manually setting the zones in secpol.msc resolved the issue, but I would like to know what caused the problem in the first place, so we might prevent it in the future.