rdiff-backup on a specific nic card?

I have lots of data that will be backed up across servers and I don't want this affecting the performance of my websites and stuff I have happening specifically on other nic devices so is it possible to specify which nic I want to do the backups on?

 

I guess you're using different networks then? The backup will then happen over the NIC that is in the same network as the backup server.

 

How does rdiff know which card to use given I have a few on the same network?

 

I don't understand why you have multiple NICs on the same network? Are you talking about real NICs or virtual ones?