GRE encapsulation in Linux: point-to-multipoint tunnels

gistfile1.txt

HUB:
 - Create the tunnel interface
       tunnels:
        mgre0:
            mode: gre
            remote: 0.0.0.0
            local: 172.31.192.10
            addresses:
                - "192.168.0.100/24"
            mtu: 1476
            
 - Let the HUB know about the spokes [one line for each spoke]
        ip neigh add x.x.x.x lladdr y.y.y.y dev mgre0
                [tunnel address] [public IP address]
                
SPOKEs:
 - Create the tunnel interface
    tunnels:
        mgre0:
            mode: gre
            remote: y.y.y.y [public IP address of the HUB]
            local: 172.31.193.10
            addresses:
                - "192.168.0.101/24"
            mtu: 1476
          

 - Let the SPOKE know about the HUB
ip neigh add 192.168.0.100 lladdr 54.175.62.164 dev mgre0
           [tunnel address of the HUB] [public IP address of the HUB]

Configure routing as appropriate.