This package contains integration scripts for configuring vlan interfaces via ifupdown (/etc/network/interfaces). For further details see vlan-interfaces(5) man page in this package.
Please note that these integration scripts only supports a limited set of interface naming schemes, which means you might be better off with writing your own ifupdown hooks using ip(route2) directly in /etc/network/interfaces rather than using this package.
It currently also ships a wrapper script for backwards compatibility called vconfig, that replaces the old deprecated vconfig program with translations to ip(route2) commands. This compatibility shim might be dropped in future releases, please use ip(route2) commands directly.
Your kernel needs vlan support for this to work, see "modinfo 8021q".