Selective programming of forwarding hardware in a multi-fabric overlay network

A non-transitory computer-readable storage medium comprising instructions that when executed cause a network device in a first fabric of an overlay network to:

• receive, at the network device, a route advertisement from a border device via which the network device communicates outside of the first fabric, the route advertisement including a prefix route for a host device connected to a second fabric of the overlay network;
• determine, based on an indicator in the route advertisement, whether a host route corresponding to the prefix route and associated with the host device is included in the route advertisement, the indicator settable by the border device to a first value to indicate that the host route is included in the route advertisement, and to a second value to indicate that the host route is not included in the route advertisement;
• based on determining that the host route is included in the route advertisement responsive to the indicator being set to the first value:
• store the host route in an entry of a routing data structure on the network device, the entry of the routing data structure further indicating the border device as a next-hop device for forwarding a packet destined to the host device and received at the network device;
• and
• program the prefix route in an entry of forwarding hardware of the network device, the entry of the forwarding hardware further indicating the border device as the next-hop device.

A network device, comprising:

• a processor;
• forwarding hardware;
• and
• a non-transitory computer-readable storage medium storing instructions that when executed on the processor cause the network device in a first fabric to:
• receive, at the network device, a route advertisement from a border device via which the network device communicates outside of the first fabric, the route advertisement including a prefix route for a host device connected to a second fabric;
• determine, based on an indicator in the route advertisement, whether a host route corresponding to the prefix route and associated with the host device is included in the route advertisement, the indicator settable by the border device to a first value to indicate that the host route is included in the route advertisement, and to a second value to indicate that the host route is not included in the route advertisement;
• based on determining that the host route is included in the route advertisement responsive to the indicator being set to the first value:
• store the host route in an entry of a data structure on the network device, the entry of the data structure further indicating the border device as a next-hop device for forwarding a packet destined to the host device and received at the network device;
• and
• program the prefix route in an entry of forwarding hardware of the network device, the entry of the forwarding hardware further indicating the border device as the next-hop device.