Enable scaling for stretched VXLAN campus networks

To support large-scaled stretched VXLAN campus networks, we provide routing policy options, sample routing policies, and new statements to optimize how host routes are managed across the access, distribution, and core layers.

With this feature, you can configure the network to install host routes in the core layer but not advertise the host routes to the distribution and access layers. The core devices advertise only subnet routes (using EVPN Type 5 routes) to the distribution devices. The distribution devices then advertise the subnet routes to the access layer. The configuration includes policies to ensure the EVPN Type 5 subnet routes are the preferred routes on the distribution and access layer devices. This design reduces the route table burden on access and distribution devices, enabling greater scalability.