All three IPs are subnetted so that each has its own gateway. default route to one of the gateways only works for the corresponding IP address and not for the other two. So I cannot route all three to a single gateway.
Will this work with the ASA?
Before we used to be able to route all static IP addresses to of the gateways...
Could you please elaborate on this part, or at least share the IPs with us ?
Normally if your ISP assign you 3 subnets, it should be a sub allocation of a bigger subnet & the routing will occur at layer2.