Ok, got it to work, “something” changed the subnet masks of my additional interfaces. And i had to adjust the interface order.
For those who are interested, here is how to configure a multihomed Windows backup server:
- Team your adapters if you want link aggregation. Configure your switch accordingly
- Put the switch interface(s) into all VLANs you need (the networks where you want backup)
- Create your virtual interfaces and assign the VLAN IDs
- On the “main” interface (the server network), assign IP Address, Gateway, DNS Servers etc.
- On all other interfaces (used for backup, only assign IP and subnet mask, nothing else. Additionally disable LMHOSTS resolution
- Change network interface order to: main interface on top,followed by the additional interfaces, then physical interfaces
- You do not need DNS records for the additional virtual interfaces