Configuring Multiple NICs on Windows 2008 Server for Network Backup
Solution 1:
You make sure your backup server can reach the file server via its IP on the separate NIC and then your backup scripts / settings must point to the IP of the new NIC.
Easy.
Solution 2:
Anand, you could try this by adding static route from your Windows Server to backup server. Let's assume your Windows server primary NIC is 192.168.10.9 and your secondary 192.168.10.10; while your backup is 192.168.1.100;
Then you could add this static route:
route add 192.168.1.100/32 192.168.10.10 metric 10
Low metric value would force this 1:1 route to be primary path for ethernet packets.