How unnumbered interfaces work
Basic IP unnumbered interface configuration illustrates how unnumbered interfaces work. A router called VR1 contains an interface named A that faces an interfaced named B on a router called VR2. A VLAN subinterface of A connects to a VLAN subinterface of B.The VLAN subinterface of A is configured as unnumbered.
On VR1, the administrator configures a static route through A toward the subnet in B. The static route makes the router take the manually configured unnumbered interface as the entry for routing, thereby, bypassing the need for a dynamic protocol to route traffic.