"Max retries exceeded to host" Reduce qty retries?

I have my dialplan configured to automatically failover to another provider in the event that one of them has issues. When this happens, outgoing calls will hang for about 30 seconds before giving up with the message “Max retries exceeded to host” and then trying the next trunk. How do I reduce the number of retries so this failover happens more quickly? (I’m using IAX, for outbound trunking, if that matters).