"In inter-VLAN routing, the router interfaces are connected to switch trunk ports. The router interfaces or sub interfaces must be running a trunking protocol either ISL or 802.1Q." Is this always a must? It makes sense if we use one physical interface with many sub-interfaces on a router for each VLAN. If we use multiple dedicated physical interfaces connected to each VLAN, Do we still need to connect those ports to trunk ports on switches? In that case, will different VLAN act like different networks that are connected to a router (just like there is nothing about VLAN)? Does it work the same in both configurations: with/without trunking port protocol enabled? Is there any performance drop if VLAN trunking is used? Which way is recommended?