You can disable RIP on a point-to-point link through the file /etc/gateways. This file does not come with your operating system: you must create it with a text editor.
To turn off RIP, /etc/gateways must have the following entry:
where ipdptpn represents the device name of the point-to-point PPP interface used.
For more information, refer to the in.routed(1M) man page.