Cacti requests sourced from loopback address?

[feet]

We have cacti running on a multi homed host. I need to have cacti send all of its polling requests from it's loopback address, rather than the ethernet address the traffic exits the box on.

This is because only the loopback can actually poll the routers on the network. Is there a configuration command or setting to force cacti to use a source ip of it's loopback? (i've put a public IP on the loopback)