SDWAN Tunnels between HUBs

Hi,

  We have 2 iBGP RR (DC and DR)acting as HUB for all the spokes. All the HUB and spoke devices has both internet and MPLS link. Few spoke has only internet links. Now I want to advertise DC network to DR as a backup route so that in case a spoke which has only internet can reach to DC in case of DC internet link goes down. To achieve this, I am planning to create an ipsec tunnel between DC & DR and configure them as iBGP neighbours. Since both DC and DR act as RR server whether DC can advertise its LAN subnet to DR which then DR will advertise to the spokes as a backup path??. What is the best practise to be followed for creating an SDWAN overlay tunnels between Hubs of the same region?

Regards

Raja