An engineer configures two IPsec VTI tunnels from a Cisco IOS XE router to an Azure VPN gateway that operates in active-active mode. Both eBGP sessions to the Azure gateway instances are established, and both are receiving the same Azure VNet prefix (10.20.0.0/16). However, 'show ip route 10.20.0.0' displays only a single next hop, and traffic is not load-sharing across both tunnels. IPsec and BGP are otherwise healthy. Which configuration change on the IOS XE router will enable traffic to use both tunnels?