router - Can not create sub-interface in Cisco CGR 1240 - Server Fault
Configure Subinterfaces and 802.1Q Inter-VLAN routing for the Cisco CCNA - YouTube
ICTechNotes: Inter-VLAN Routing
Example for Configuring Sub-interfaces to Implement Inter-VLAN Communication - AR100-S, AR110-S, AR120-S, AR150-S, AR160-S, AR200-S, AR1200-S, AR2200-S, and AR3200-S CLI-based Typical Configuration Examples - Huawei