I would like to setup the following configuration:

2 servers with 1Gb NICs connected to a GB switch

client PCs connected to 100Mb switch

1 Backup server with a tape drive. This will have one 1Gb NIC
connected to the Gb switch, and one nic connected to the 100Mb switch.

I need to connect to the backup server from my client PC through the
100Mb channel. I would like the servers backed up to the backup
server through the 1Gb channel.

How should this be configured? How does the backup know to send data
through the 1Gb channel and not the 100Mb channel?

Sorry if I havent explained this too well!