The second topology is based on BGP EVPN, as shown in Figure 3. The leaf pair in the VLT mode, hosts a single VTEP. The AWS Outposts network devices OND1/2 still does the BGP peering with the Leaf1/2. The VTEP on Leaf1/2 takes the learned routes from AWS Outposts and advertises it into the EVPN fabric using Type-5 routes. Other VTEPs in the data center will know how to access the AWS Outposts infrastructure.
Figure 3 shows how the border leaf performs the same eBGP peering with the WAN router, and re-advertises them into the EVPN fabric as Type-5 routes. The end devices in the EVPN fabric can now access an outside network including the AWS Outposts devices.
Additional information on the example design: