Hi Simon,
Yes I understand that enabling that option would stop any client only on the production network from 'working'.
However, this option is a necessity as the previous DNS configuration, regarding Master & Media servers is an unknown. Present DNS administartors assure me that DNS (and NBU servers entries) is configured correctly. If the specificed network interface is not set to the backup environment NIC, then backups which use the backup network will fail.
I know this is a DNS type issue but cannot determine how it was previously configured. NBU documentation points towards using specified NIC to ensure the backup network is used as a priority.
BTW, nice to hear from you.