bind RIP protocol to specified address

Hi all. I use bird2 (2.0.7) on linux, I want to configure the RIP protocol so that it uses the specified source address. I have two addresses assigned on the network interface, for example 192.0.2.1/32 and 198.51.100.1/31. bird chooses 192.0.2.1 as the source address, but I want the source address to be 198.51.100.1. How do I set the source address for the RIP protocol ? Thank you.