Differences between router interfaces and subinterfaces
Cisco router setup sub interface for intervlan routing - YouTube
Example for Configuring Sub-interfaces to Implement Inter-VLAN Communication - AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 CLI-based Typical Configuration Examples - Huawei
How-to Configure Router on a Stick - Cisco
Physical Interface VS Multipoint Subinterface in Cisco Frame Relay - Server Fault
How to Configure VLAN subinterfaces on Cisco ASA 5500 Firewall