neutron-lib/api-ref/source/v2/samples/routers/router-remove-extraroutes-request.json

{
   "router" : {
      "routes" : [
         { "destination" : "10.0.3.0/24", "nexthop" : "10.0.0.13" },
         { "destination" : "10.0.4.0/24", "nexthop" : "10.0.0.14" }
      ]
   }
}