Trunk Failover when CHANUNAVAIL (subscriber absent) Not Working

I have two trunks specified for an outbound route, if one returns “Unable to create channel of type ‘SIP’ (cause 20 - Subscriber absent)” it doesn’t failover to the next trunk? Is this expected, I thought if the trunk was down or unavailable the call would failover to the trunk?


Does any know this?

Is just a case that failover to another trunk only occurs on congestion?