its little bit difficult, if primary to datacenter and secondary to broadband we could have make it by advertising default route with higher metric from bgp to eigrp and static default route towards dia with less metric, if bgp goes down you dont have dynamic default route in your routing table and option is only static default, so traffic will go to dia.
as per my expertise you could make it your goal by adding internet loadbalancer you have to place it in a way that one of its connection goes to l3 switches for lan traffic and for wan one connection to dia lan interface and one connection to your router 2 lan interface. in router 2 you have default route coming from bgp this you dont need to advertise to your eigrp, simply add static default route in l3 switches towards your internet load balancer so that failover or load balancing will be take care by load balancer.
in load balancer you can create a rule that if DIA goes down internet traffic should go to another interface which is connected to router 2 , here in router 2 you already have default route which is coming from bgp. so traffic will forward to datacenter.
in router 2 what you have to do is, you check if any extra routed interface available. if available you just take /30 from your organisation private pool configure one ip to router2 and one ip to load balancer, second step in router 2 is redistribute this newly created /30 into your bgp so that traffic reaches from datacener to your router2.
in router2 if you dont have routed interface and switch interface is availble you can make a routed connection to your load balanver by sub interface or using vlan interfac
if you dont have any interface available you can buy hwic card so that you have some interfaces.
for your scenario best load balancer is cyberoam 25ia and it is very cheap.
thanks
Shaik Raffath
