As illustrated in Figure 1, a level 1 parent route is a level 1 network route that is subnetted. A parent route can never be an ultimate route.
Figure 2 highlights the level 1 parent routes in the routing table of R1. In the routing table, it basically provides a heading for the specific subnets it contains. Each entry displays the classful network address, the number of subnets and the number of different subnet masks that the classful address has been subdivided into.